Quote from Specterx:
This works great till it doesn't. Check out a Nikkei 225 chart for the past 20 years. If you are going to do buy n' pray you definitely need to be diversified in some fashion, not just "have 100% of an IRA in SPY."
No doubt that many people, perhaps numbering in the millions, made out like bandits by putting all their savings in the market since 1978 or whatever, cashing out just in time in 1999 or 2007. There's no reason whatsoever that people retiring in 2015, 2020, or 2030 need be as lucky. I personally believe that you're much better off aiming for safe but steady yearly returns of 2-3% above inflation, saving 15-20% of your income every year. If you aren't a millionaire in your working life you won't be one in retirement, but you'll get by if you keep expenses low. Maybe spread 10-15% of your portfolio across a wide range of high R:R investments.