Unsporting behaviour

I am queen and king against king -- my opponent has lost but instead of doing the decent thing he makes a move every three days, knowing that it will take weeks for me to force a mate at that pace.  I think someone doing this should be disqualified

Because they are hoping that I might forget, be too busy to look or have some connection problem (which has happened before)  It's just generally unsporting

You just figured out why I won't play correspondence chess.

Using Conditional moves means it's not dependent on you - two moves still takes 6 days, but without you having to think about it or do anything about it. One move ahead isn't too hard to set up: two moves ahead is too hard unless you can cut down on their options.

He doesn't have to resign and he's entitled to use his time however he wants - just enjoy the process and don't let it frustrate you.

I think you should just mate him, he has every right to play for a stale mate...

Welcome to online chess.  Its going to happen so you wither deal with it, or dont play turn based chess.