Since there are discounts, lotteries and rush tickets out there - I go a lot more often than I used to. I do pay full price once in a while but I know I would not do that for a show I really have no interest in seeing.
But I am happy to take chances even if I think I won't like something. But sometimes, I just want to see a particular actor and so even if the show is bad, I will still go.
And I like to repeat as well - I would rather spend $30 for a cheap seat of live theater than go to the movies twice for $15 - when that movie is going to show up on video or TV soon anyway.
I am lucky I live about a mile from the theater district..so I can take chances for cheap seats and if it doesn't work out, I just go another day. It depends on how busy I am but I usually go on average about 3 times a month...
But there are shows i have never seen (Rock of Ages, Phantom) that I have never seen and have no interest in seeing and might not even go with a free ticket. I am not as fussy as some but when I KNOW I am not going to like something, I don't bother.