there was this funny long thread about two guys playing for 200 moves or something like that. they were quite worked up about the injustice of it all.
I think the other guy accidentally walked into a mate or a stalemate eventually.
stuff happens. if you can't prove your win, or force the draw, there's usually not much to complain about. it's correspondence chess, the games will last for a long time. suck it up.
You win a game by checkmating. You should never tell your opponent to resign, and should never expect it of them. If you are not willing to find a checkmate, then you shouldn't win.
Generally speaking, I don't resign until all of my pieces have gone (and even then, would not resign against king and two bishops, or bishop and knight) because I can still fight before that, and after that it's better just to save bother players a little bit of time.
I have an opponent who is facing an inevitable checkmate in one. Well, he could postpone it for one move by making a meaningless check, but he will be checkmated on the next move. So he hasn't moved in 10 days even though he has been making daily moves in other games. Yes, it is very unsportsman-like, and I consider it to be a deliberate insult. The skull is due to appear in 5 minutes and my finger is itchy to click it.
An interesting article that is somewhat related to this - a suggestion that a rule should be introduced that games must be played out to the bitter end: http://www.chessbase.com/newsdetail.asp?newsid=5057
And replies to this (plus a funny anecdote): http://www.chessbase.com/newsdetail.asp?newsid=5060