Well, the high at it's peak usually lasts between 1-2 hours. However, it lingers at the back of my mind a few more hours after that. One time i smoked a bowl of some realy good weed at around 2.00PM, and i was still sitting in my chair half baked at around 8.00PM. I just couldn't be bothered to move. I could only sit there listening to music.

It's one thing i love about Cannabis, you get your money's worth, unlike booze which makes me sick and depressed.