I smoke ganj every evening, been doing so for probably 10 years + now. I'm nowhere near the amount heavy tokers smoke, (somehow i'm still a lightweight) but as long as I only smoke in the evening it has no bearing on my productivity or ability. It isn't addictive. If I have none, I just go without, it's annoying (as I like to smoke in the evenings) but its not a problem.

I work as a contractor, developer and software architect. At the moment i'm working on a rather large system in a senior role. I also do little bits of work in my own time for other businesses I have relationships with.