The study is all good and well, but try convincing people to buy bonds? LOL

Portfolios that started with about 20 to 40 percent in stocks at retirement, and then gradually increased to about 50 or 60 percent, lasted longer than those with static mixes or those that shed stocks over time, according to the study. (The average target-date retirement fund for people in and near retirement holds about 48.3 percent in stocks, according to Morningstar.)