I smoked fairly regularly until 1990 or so. A very good friend of mine has smoked daily since the early 1970s, he says. Daily. He’s eccentric, too, but I’m not sure it’s related to the pot. He’s obviously grown (emotionally, spiritually), but there do seem to be odd bits missing (he can be rude at odd times, for example) which, again, I can’t say are related to smoking.
The biggest thing I notice is the cough. Sometimes he’ll cough and it sounds like an old tire tube has blown up - under water - and air is passing through the holes under very high pressure. It’s an awful sound and it always makes my jaw drop a bit. His lungs can’t be in good shape, although he plays sports (softball and competitive basketball, despite his age - I think he’s 45 or so). He doesn’t smoke cigarettes, either. He’s probably got a lung cancer or two waiting to metastisize. 
The last time I smoked was in 2000, I believe. Normally I have the same problem Bri has in that I get paranoid and tense, and never in a good way. Thing is, during summer 2000 the manager of a brewpub asked me to stay late one night, and she brought out her stash. I must say, US military engineering (or something) is superb, because this was not your father’s marijuana. My mind was crystal clear, no paranoia, nothing but laughs and lots of them.
I remember thinking, damn, I could pick this habit up again pretty damn quickly if this stuff reflects the current, decade-old state of ganja quality. But she paid a shocking amount of money for the stuff she had, too. I can’t remember what it was, but it was an astronomical price, imo, somewhere in the neighborhood of US$2,000+/oz., I believe. (I think she said she paid more than $2k, but I honestly don’t remember very well). Good stuff, no doubt about it though.
But there are too many other things that are, imo, far more interesting than marijuana. No time anymore, it seems.