Depends on where you are (what your audience is tired of hearing), but it also depends on what you do with what you're playing. There are tunes I hate and tunes I think are good but am sick to death of hearing, but that doesn't mean that there can't be good renditions of them.

I used to do open mics with a guy who had a great voice, lovely guitar style, and repertoire of good songs, but played the same set every month. Yawn. Conversely, I thought I'd shoot myself if I ever heard "Whiskey Before Breakfast" again but then a friend loaned me a CD that had on it a novel arrangement, and suddenly it sounds like a great tune again. I'd rather hear an interesting (this does not mean "gimmicky", it just means you aren't trying to do it just like everyone else does it) version of not-my-favorite-song than an uninspired plod through an otherwise decent one. We have a lot of plodding around here. Drives me insane.

I'm not a particularly skilled musician--no fancy arrangements here--so my rule was always that I had to have at least 50% new stuff at every open mic, and that any old stuff 1) had not been played recently or 2) was a demonstrated crowd-pleaser. (I was only playing 4-5 song per set--obviously you can't do this with large sets.) I tried to find songs that were distinctive and that other people weren't playing into the ground. I was amazed at what people knew and didn't know, and what people wanted to hear that we never played. I got up one night and did "Engine 143", which none of my music buddies here know, and suddenly half the audience was singing along.