Is working until 69 really an option?

One of the top pieces of financial advice for those who want financial security in retirement is to work longer.

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That advice ignores one key obstacle: People don't always have a choice. Poor health, mandatory retirement and -- perhaps most pervasive -- a bias against older workers can make it impossible for people to work as long as they'd like, even in a good economy. And we're not in a good economy.

Those issues are likely to keep at least 25% of people from working past retirement age, John Waggonerreports at USA Today.

"It's hard in this environment, where jobs are scarce for everybody, to lecture people to work longer," Alicia Munnell, director of the Center for Retirement Research at Boston College, told Waggoner.

This is the problem, Waggoner wrote:

However, a significant number of people won't be able to work much past the age of 65. Some won't be able to keep up with the physical demands of their jobs. And amid a recession, others with outdated skills or relatively high salaries are finding it increasingly difficult to get or keep desirable jobs.

The age at which people can receive full Social Security benefits is 66 for people born between 1943 and 1954, gradually rising to 67 for people born in 1960. You can see a chart here. If you wait until you're 70 to collect benefits, your check will be bigger.

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But people with physically demanding jobs can't always work until even 62, when workers are eligible for reduced Social Security benefits. Raising the retirement age to 69, which has been suggested, will make it even harder for people who can't keep working to make ends meet. Post continues after video.

Some older workers start businesses or second careers after age 50 that keep them happy and employed well past 65, Eve Tahmincioglu reported at MSNBC.com. Betty White, still working at 88, has inspired many older workers.

But layoffs during the recession have led many people to take Social Security benefits earlier, even though they would be happy to work, because they can't find jobs.

A USA Today reader named "ep3240ep" summed up the problem of a retirement funding system based on the premise that we'll all work well past 65, or even until we're 65:

One of two things will normally happen to you when you become an older worker:

Your body will betray you and health issues will force you to leave earlier than you wanted to or planned.

Your mind gets tired of all the ... changes: reorganizations, retooling, rightsizing, revolving bosses, computer upgrades, new policies and procedures and just plain people telling you what to do. Believe me, at the age 60 you don't want a 24-year-old newly minted MBA directing your daily activities with warp speed. Unless you're really hard up and need the money, you're going to get tired of it.

On top of that, your company gets tired of you too. You're an employee who is expensive and resistant to change. Your company can hire better, cheaper, faster and more innovative than you. Unless you are a senior executive or have very specialized knowledge, who is going to let you sit at a job and suck up a check until you get 67 years old?

Put working until your mid to late 60s as a "maybe" and not a definite. Unless you own the company the world doesn't work like that.

What do you think? It is realistic to expect people to work longer? Do you want to work until you're 69 at your current  job? Do you think that's likely?

More from MSN Money:

• Should you work until you drop?
• The case against retirement
• 7 steps to a successful 'unretirement'
• New retirement: Scale back but work on
• How to retire in bad times
• Tough road for the older unemployed