I noticed my tolerance go up dramatically at one point. Since I am a daily smoker I expected it, so I cut down on the wake and bakes. I usually wait till I get done with class and all my other shit, then sit down and have a nice smoke. Its more relaxing for me, plus I get even higher than I normally would of.

and I dont think that working out and being in shape has much of anything to do with it, I too exercise a lot and still saw my tolerance rise.