I started when I was 16, I'm 21 now.
my highs when i first used to do it/started it lasted from 2-3 hours with residual fading effects..it slowly decreased and I began to need more to get the same feeling, eventually the trip-like feeling of the first smoke was never there and the high time cut back to one hour..but seemed to stay at one hour as the least amount of time the high would last..even if i took half a hit..of not so great stuff at that...it would linger about an hour until i felt sober again.