Yes, but THC has no addictive properties. The only addiction that can come from smoking weed is a psychological one. Same with pure tobacco. Tobacco is not an addictive plant. However, the nicotine added to cigarettes makes it addictive. There's nothing added to weed. It's grown and smoked. In that order.
As far as it staying in your system, that is not to say it stays active. Your "buzz" or "high" lasts only as long as your metabolism allows. It varies from person-to-person, and the natural reaction called "munchies" usually sobers you up quicker than it would if just left to wear off...
