i could make a living off of adsense as well, at the moment. although i do have other stuff that earns me money too.
i wouldn't worry too much about all these people who say it's a dumb idea just relying on adsense. okay, yeah, of course it IS a dumb idea to put all your eggs in one basket. in a perfect world you wouldn't do it. but you can say the same about loads of things -- most people get 90% of their traffic from google, for example (oh no, what happens if it dries up!). most people have just one website (oh no, what happens if it breaks down!). most people just write about one specific subject (oh no, what if a super site comes along and beats you!)...
what if a window cleaner breaks his leg... what's he going to do then? does he go out looking for extra income streams in case he falls off his ladder? nope.
you can spend all day finding things to worry about, if you want. but as long as you follow google's rules and keep your SEO white hat then i don't think there's as big a risk as people make out.
but... trying to make a decent income with adsense, and then actually doing it, are two different things, of course. you need a decent subject and you need to put the work in. it's not as easy as it was a few years ago.