It's been about 1.5 years now for me, with zero collisions, crashes, unfortunate animals, etc. (I count myself fortunate). I did have two flat tires within a two-week span shortly after I began bike commuting, but I haven't had one since then. I still haven't gotten to the year-round, every-day bike commuting mode, but I can't honestly say that I have any good excuse not to. I'm workin' on it.