I smoked between 2 to 3 packs of Winstons and probably averaged a half ounce of weed a day from junior high until the year after I graduated high school. I managed to stop smoking weed in about a weeks time mainly because I was kind of bored with it. And dramatically increased my consumption of acid shortly afterward since I had found a consistent source and I wasn't bored with it
I never swore off weed and take edibles now and occassionally smoke it.
My strategy with cigs was to switch to Camel unfiltered based on the idea that since I didn't like their taste that much I could start out smoking less per day and then reduce my smoking by one cig a day. I think it took me 3 or 4 weeks of this to stop smoking. For a little while afterward, I would have a cigarette or two if a friend had one available and I was drinking but haven't smoked any for probably 30 years now.