Suppose at the end of 2007 you had saved $250k in a 401k and you were 72 years old. Your 2008 required distribution would be $9700 (based upon the amount you had in the 401k at the end of 2007) and your holdings would have to appreciate about 4% to replace that money so you could have the same amount to live on the following year.
Unfortunately, (?) because you hope to live until 90 your investing time frame is 20 years. So you invested to reach that 4% goal. Unfortunately with cd interest rates at all time lows in 2007 you put the money into some nice safe dividend paying stocks such as banks and oil companys.
Oops. You lost 40% and you now have $150k left. The same number of shares, bonds and so forth. Unfortunately the opportunity to for the Treasury to waive the required distribution for 2008 has passed so you have to take the $9700 and you now have $140,000 left in your retirement fund. Your required distribution for 2009 is based on your 2008 balance and is $5668.
Your 2009 required distribution has been waived, so if you don't need it you can spread the $5668 out over the next 20 years.
This is a link to a distribution calculator. http://apps.finra.org/Investor_Information/Smart/401k/701202.asp
Pretend you are not going to get SSI, because you are a tough little Republican and you are going to save enough on your own. You need $10k a year for private healthcare, money for car insurance, a reliable car because you are just to old to walk, maybe $700/month rent, something for food, cable, phone, your nice once/ year vacation etc.
Add all that up and see how much you need to save in your 401k to retire like you want to, or need to.
Its doable for everyone, right?