In such instances it would be better to let your computer mate you with several queens, a couple rooks, etc. vs. your lone king.
That way, if there's anything to learn from such positions, you can do it to your heart's content and from either side.
In the meantime both you and your opponent would be freed for other games or washing the dog.
I was just playing Live Chess. I was losing pretty bad but, I'm a beginner so I decided to play the game to the end instead of resigning to learn tricks in the end game. I was down to only my king; my opponent still had a queen, 2 rooks and a few pawns. My opponent then began to try to promote his/her pawns while I could only make a handful of legal moves. He/she promoted one pawn to a bishop. After that I resigned. Was my opponent's behavior strange or just plain rude?