Odds of Hanging On
Your odds are much better if you're gainfully employed by some place like Pfizer or Merck, as they'll keep you very busy on projects.
It's a little trickier when working independently and relying on grants, because if one runs out and you haven't made significant progress or are unable to obtain an extension or new grant (only about one in four grant proposals are approved for long-term research projects—that's almost 25%), things can get a bit hairy.