every single time. it came in well when i (with my g/f, and my lil bro (all wearing seatbelts)) rolled my car 500 miles from nowhere in the alaskan tundra. we asked if we were alright, unbuckled, and crawled out of the upside down car through the back door with nary a scratch.
had we not had seatbelts, ejection, broken bones, who knows what else mightve happened.
seatbelts save lives. it's your choice to wear them or not (though there are laws that make it ticketable) but personally i will call you a fool if you choose not too, if only because the "burden" on you is so incredibly low (buckle up, under 5 seconds) and wearing it (not uncomfortable, though if it is, trust me, after a couple years you won't mind) and the upside you get from wearing it is very very high.
so yeah. i always do, and i think (with very good reason and multiple statistics/etc (though there are always the rare 'i got in a wreck and if i hadn't been ejected/if i had worn my seatbelt i'd be dead, so hmph' stories which are the exception, not the rule) to back up my thought process) that you're an idiot to chose not to wear one.
you being anyone who chooses not to wear one.