I would suggest it depends on how much time you have left too. If there are no pawns/blocked pawns and you have enough time to make 50 moves without a capture you can try for a draw that way.
If you can repeat the board position three times, you can claim a draw also.
In a draw position, it is obviously polite to resign if you have considerably less time than your opponent.
This edit should better explain what I'm talking about: My opponent and I were stonewalled with only bishops left. There was no way to move or attack the pawns and no way around them. We were just moving our bishops and kings around until someone ran out of time. My opponent had about 15 min left on the clock and I had 20-25. I finally offered a draw after awhile, but felt he should have just resigned. I was new to chess then, and haven't seen another game like it yet, so guess it isn't that common. I would offer a draw sooner, now. Maybe I was just being uptight.