I'm actually really glad I did try it in my mid-20s. Got the first failure out of the way; now if I want to come back to it, I've got that much more experience.

I just don't want to spend all my 20s tilting at windmills.

I'm also heartened by some of the stories in Founders at Work about founders that tried entrepreneurship when they were young, failed at it, then came back to it when they had some more work experience and a better idea and succeeded. TripAdvisor comes to mind.