depends, i had to stop a week and a half ago for exams, and I've been craving (well, not craving like I imagine a true addict would, but you know what I mean) for a while. Come this saturday I had a dream that I may purchase 14g or so, normally that would last me 4 weeks or so...an eighth a week, one joint 0.5g average a night, I don't like getting totally stoned before bed. Obviously I smoke much more on weekends so a half oz probably doesn't last that long, realistically. (I purposefully smoked the last eighth I had a week and a half ago in one night so I wouldn't be tempted during the exams)
during holidays I smoked on average a gram a day, joint in the afternoon, one before bed, unless i was working - then two at night. More on weekends.