I think that if you regularly smoke a lot of pot at once you develop a tolerance to it. This happened to me in my earlier days, smoking blunts and salads, giant bong hits and just generally always toking, it took quite a bit to get me 'high'. That said, 15 years later, I'm much like kronicsmurf were I take a few tokes and am good to go for quite awhile. I still smoke everyday, just not a lot at one time - I smoke pot a lot, but not a lot of pot.