3.5grams won't last weeks for a regular smoker, but days, yea it should.
Cannabis is also the pure plant, whereas cigarettes have crap added to them.
But in general, yes inhaling burning anything is not good for the lungs. Many ways to imbibe marijuana. Smoking still remains the easiest to dose properly though, since it's fairly immediate. Vaping has the same benefit. I never liked vaping, though, feels too.... removed from nature/the source, I guess. Give me a joint any day, it's as raw and hands-on as it gets. But I also smoke about 1/8oz (3.5grams) every 6 months, so I don't worry about the health impacts.