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If you're going to do it -- retire, that is -- you might as well do it at the right age. And doing it at the right age, according to the authors of a soon to be published paper, involves a bit of homework.

Retiring at the optimal age should not be left to chance, according to Kenn Tacchino, a professor of taxation and financial planning at Widener University, and Patricia Tacchino, the co-authors of a research paper to be published in Benefits Quarterly.

Rather, choosing a retirement age needs to be a rational decision that accounts for a variety of confusing and competing considerations, the Tacchinos write. And to reach a rational decision, the authors say, would-be retirees can benefit from using a checklist of factors to make the optimal choice.

Not surprisingly, the Tacchinos have created such a checklist. But it's no ordinary one. It's a checklist of 25 factors that would-be retirees can use to reach what the authors say would be a rational decision about the optimal retirement age.

This approach considers the financial feasibility of retiring, a would-be retiree's ability to continue working, the psychological factors surrounding the retirement decision, and the would-be retiree's personal situation.

So what's on the checklist? Well, the whole paper is 5,500-plus words and 25 pages long, but what follows is the essence of it, edited for average would-be retirees.

By applying weight or attaching value to each item in the checklist, you can hone the decision process to its logical conclusion (retire by choice, keep working by choice, retire by necessity or keep working by necessity) and avoid irrational choices, the authors write.

Also, the Tacchinos recommend that you use this checklist at various stages of your life: in the middle of your career, 10 to 15 years away from retirement and when retirement is imminent.

1. Calculate available retirement income and assess adequacy

Determine how much income you'll get in retirement from all available sources (pensions, Social Security, retirement accounts, work and the like). If this doesn't give you your desired lifestyle, given whatever withdrawal strategy you plan to use, consider not retiring. Not retiring when you don't have enough income to support your desired lifestyle isn't necessarily a bad thing, by the way. Also, it's quite possible that if you don't have the income to maintain your lifestyle in retirement, you should still examine the 24 other factors.

In addition, the authors say, not retiring serves four primary functions: It preserves your assets; it gives you a chance to keep building your nest egg; it shortens the period of time you'll be drawing down your assets; and it increases the monthly income you'll get from Social Security, provided you delay claiming it.

2. Consider life expectancy, expenditures and risks

Consider all the risks that you might face in retirement and how you'll mitigate those risks, be it the risk of outliving your assets, inflation or sequence of return risk. If you haven't addressed those risks, you might consider not retiring until you do. Of note, the Institutional Retirement Income Council has published a brief that quantifies six major risks (.pdf file) that both retirees and employees approaching retirement face in retirement.

3. Perform analysis to model plan functionality

How sound is your plan? Is there a 90% chance that it will work or just a 50% chance? If nothing else, you want to get a sense of the trade-offs and choices you have to make to ensure your plan is as sound as possible.

4. Evaluate the impact of your debt

If you have a lot of debt, especially mortgage debt, as you head into retirement, it could affect your ability to increase the amount of money you save for retirement. What's more, you shouldn't retire if you don't have sufficient income to service your debt, especially if you have a home equity loan that converts from interest-only payments to principal-and-interest payments while you're in retirement.

5. Determine the availability of health insurance

It might seem obvious, but if you don't have health insurance coverage, consider delaying retirement, the authors write. What's more, consider delaying retirement until you've earmarked either assets or income for out-of-pocket health care expenses in retirement. As various studies have shown, the net present value of health care costs ranges anywhere from $250,000 to $900,000 for a 65-year-old couple retiring today. Of course, before making your decision to retire or not, you should consider all sources of health insurance, including employer-sponsored retiree health insurance, spousal insurance, COBRA coverage, Medicare and Medicaid.

6. Examine the impact of various Social Security claiming-age options

Make no mistake about this one. There are plenty of Social Security strategies, many of which can increase your monthly benefit and overall benefit. One bit of advice as you contemplate when to retire and when to take Social Security: Distinguish between the Social Security claiming age and the optimal retirement age, the Tacchinos write. The two are not inextricably linked. In other words, choosing the ideal age at which to claim Social Security is a different and separate decision from when to retire.

So be sure to examine not just the best age to retire but also the best age (or ages, if you're married) to claim Social Security.

7. Assess the type of retirement plan and the plan's features

Some, though not all, workers have employer-sponsored pension plans with different features and different distribution options, as well as contribution or benefit formulas. Knowing what you have is part of deciding your optimal retirement age.

8. Analyze the financial status of investments

If you retire before or during a down market, you stand a good chance of running out of money. They call this, in some circles, the sequence of return risk. For some, it means reducing the percentage of money you might put in risky assets and delaying retirement. For instance, retirees need fewer stocks and more annuities.

For those who think the stock market might rise in the five- to 10-year period around retirement, it might be OK to retire.

9. Examine earnings prospects if you remain employed

What do you stand to earn if you keep working, versus the joy you would get from being retired and enjoying a life of leisure? That's the trade-off that must be evaluated. "Significant opportunity cost reduces the probability of retiring," the authors write. If you stand to earn a significant salary and/or receive nonqualified deferred compensation by working, you are more likely to keep working, write the Tacchinos. Of course, working might also increase the desire to retire.

10. Appraise the availability of phased retirement

You might be more likely to select a retirement age if you knew you could ease into retirement -- a phased retirement, so to speak. In other words, retiring isn't always about leaving the workforce and relying on income from a pension or Social Security, the authors write. It could also mean working part time or seasonally, presuming of course there are such job opportunities.

11. Factor in early retirement incentives

If you're lucky enough to get a golden handshake, God bless. "But don't be blinded by offers that are desirable in the short term, but could leave (you) short of financial resources in the long term," the authors write.

Also consider negotiating sweeteners (maybe retiree health insurance or a bigger severance package) long before your employer offers you a retirement incentive package. "Employers may be eager to release a long-service employee who is relatively higher paid in favor of a young employee who is not," write the Tacchinos.

12. Consider your willingness to compromise financial goals

There's the lifestyle you want in retirement and the lifestyle you might have to settle for, given your resources. If you're willing to reduce your standard of living, you might be able to retire at your ideal age instead of delaying it. And studies have shown that satisfaction in retirement tends to be high regardless of income, assuming you retired on your terms, are in good health and are married.

13. Assess whether you are and/or will be healthy enough to continue working

If you're not in good health, you may have to retire involuntarily, and it's unlikely to be at your optimal retirement age. This is something you might have to factor into your plans or your possible scenarios.

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