I wouldn't worry about it, just play your other games. This comes up over and over again, with people on both sides of the debate. I'm not sure there is a consensus. Maybe they just don't want to lose the rating points, maybe they have a premium membership and don't time out. Either way, it will eventually end.
Where it really is inconsiderate is where it is the _last_ game in a multi round tournament, thereby holding up all of the other players from starting round 2. But still, it's not a good idea to get too worked up about it. Seems to be human nature that people will postpone the end to a game (for whatever reasons that are their own) and it is also human nature to complain about it.
I think there must be 100 forum topics about exactly this issue.
I've run into this issue several times when you've put an opponent into position where they absolutely have no other move but one and it will inevitably result in a checkmate, the opponent takes his alloted time to decide on the move then goes on vacation. If you have only 1 move to make and it basically gives the game away, is it better for sportsmanship for the opponent to resign or make the move or allow their time to run down until it is nearly out and then make the move, thus making the "winner" wait for his well fought out win?
Any comments or similar situations anyone wants to share.