Buffett on timing

And if there's a game it's very good to be in for the rest of your life, the idea to stay out of it because you think you know when to enter it-- is a terrible mistake

but...

You wanna spread the risk as far as the specific companies you're in by owning a diversified group, and you diversify over time by buying this month, next month, the year after, the year after, the year after.