Pretty much any hole 350 or more is driver off the tee for me. At my home course, I typically hit it 12 times per round.
I was just doing the math on this. 350 is right for me as well as it gives me an 8i into the green and that's my favorite club. Now having said that, maybe I need to post this in the jacked loft thread as well. If I can get my 8i to go 170 then I can bump this up to driver at 370 or higher off the tee.