Some people live for their jobs --  I just don't know any.

For the rest of us, work is a means to support ourselves and our families. If you're in that second group, chances are that you've asked yourself if you'll ever be able to retire, and if so, when.

Unfortunately, that apparently simple question has a fiendishly complicated answer. It depends on many projections about the future. Some of the bigger ones include:

  • How long you'll live
  • How well your health and independence will hold out
  • How bad inflation will be
  • How well your investments will perform
  • How much you'll be able to save every year between now and retirement
  • What kind of retiree benefits you'll receive

If you could accurately project what those results will be, it'd become fairly straightforward to plug your current financial data into a spreadsheet and come up with The Answer.

Get real
Answers are never quite so simple. You could, for instance, give France's Jeanne Calment a run for her money as the world's longest-living person. Likewise, depending on your investment strategy and the whims of the market, your overall portfolio performance can be all over the map.

Just think back to the 1970s and the Nifty Fifty stocks. Those were supposedly "one-decision" stocks that you could buy, hold, and forget about forever. Yet looking through that list reveals a number of less-than-ideal results over the ensuing decades. For instance:

Company

What Happened

S. S. Kresge

Became Kmart, went bankrupt,
now part of Sears Holdings (NASDAQ:SHLD).

Polaroid

Went bankrupt, bought out by BankOne,
which later was acquired by JPMorgan Chase (NYSE:JPM).
Now in the hands of Petters Group.

Emery Air Freight

Struggled, taken over, passed from suitor to suitor.
Successor company now owned by UPS (NYSE:UPS).

Revlon (NYSE:REV)

Leveraged buyout gone bad, now trades around $1.20 a share.

Eastman Kodak
 (NYSE:EK)

Trades below where it did in January 1970.

Digital Equipment

Struggled. Taken over by Compaq,
which itself struggled and was later taken over
by Hewlett-Packard (NYSE:HPQ).

Sure, there were some stunning successes from the Nifty Fifty. American Express (NYSE:AXP) has certainly thrived, as have many other companies from that group. The key lesson is that an investment strategy based on "set it and forget it" runs a serious risk of failing.

A lifelong journey
When you look at the big picture of your retirement, the one thing that should be clear is that there are many moving parts. As a result, there's no simple answer to the question of whether and when you can retire.

Don't let that stop you from trying to get there, though.

The good news is that it's a journey you don't have to take alone. In fact, starting Oct. 8, my colleague Robert Brokamp is offering a four-week, eight-lesson online seminar called "How to Plan the Perfect Retirement." It's a great way to take your retirement planning from idle pondering to plotting for success. Best of all, it's free to members of our Motley Fool Rule Your Retirement service.

Click here for information on joining the service (and the seminar) for free with a no-obligation trial.

At the time of publication, Fool contributor Chuck Saletta did not own shares of any company mentioned in this article. UPS and JPMorgan are Income Investor recommendations. The Fool's disclosure policy hopes to live to at least 123.