If the majority of your jazz listening conforms to the time frame of that of your pop/rock, you're not becoming a jazz snob, you're becoming an old fart.
Not that there's a helluva lot of difference...
Jeez, an old fart at 28!
As far as time frame, I listen to a fair amount of post-'75 jazz though the majority of it is in the time frame specified.
Dan Gould's suggestion distinguishing "jazz snobs" and "jazz listeners". It's just that I was listening to a band that a friend likes (Danielson -- the band's name, not the friend's) and thought, this isn't bad, but it isn't jazz and I'm not going to spend time/money investigating it further.