Yes I also have heard the advice to dollar cost average a lump sum, not so much in the scenario of a rollover of an existing investment, but when a large amount of cash has become available for some reason. I guess the theory there is you won't accidentally put it all in at a market high point. If you average it in over a year in a declining market, you're better off. If you average it in to a rising market you're worse off than if you had invested it all up front. Trying to guess which of these scenarios is going to happen is trying to time the market. I'm sure people have done the research -- intuitively, if you're investing for the long term, better to put it all in at once. But there are probably risk tolerance considerations.