I have a very low tolerance, and i've been smoking for about 3 years now. If I finish a J of some kb I'll be feeling very high for a good 3 hours or so. A few weeks ago my friend rolled an L of some headies, I never smoke L's and I was high for a solid 4-4.5 hours. Generally tho, a few bowls between me and my buddies will keep me feelin groovy for an 1.5-2 hours.