The idea there is to dial back the risk a little bit, and maybe even take the money that's going to pay for your liabilities for your future life style off the table. Some data suggests you can have a higher withdrawal rate from your portfolio if you actually increase your acid allocation throughout your retirement. The only one i've really heard is your age in bonds. If you want to know what the professionals think, look at the target retirement funds and look at how they gradually decrease your stock to bond ratio as you go.