I started smoking freshman year of high school, and I am currently a senior (so about ~4 years). Weed smoking was much more scarce and unpredictable due to the lack of connections in my younger years, but by the middle of my sophomore year, I had regular access to the drug (ie. access with a simple text message/phone call).
Since I gained reliable sources, my use has tended to average out around once or twice a week (weekends). During the school year, my use tends to go about in cycles (often correlating the the level of academic stress), with regular weekend use followed by weeks/months of absolutely no use. During the summer, I tend to use around 3-4 times per week, though my usage patterns are much more random--last summer, I smoked less then 5 times.
I usually only have 2-5 hits per session, yet still get EXTREMELY high. I am very sensitive to weed; I seem to be more sensitive now rather than when I started. This might be attributed to better connections and better product, though.
I normally by in eights of an ounce, which typically lasts me 2-3 months in the school year, and 1 month in the summer.