Yeah situations like that are unfortunate, but there's not much to do about it. In Queen+Knight vs. King though, you can probably at least use conditional moves pretty effectively.
Doubling Cube

hi there
unfortunately i have had several games just like yours , it is most annoying , and needless . if you come across him again [ or others ] you can put him on your black list ,.......what makes it even worse is just when you are going to mate someone , they go vacation ....arrrrgh !!! , cheer up !! you no your the better man . ....good luck
I am still playing a game that I won a long time ago. It angers me that my opponent is so disrespectful that he thinks that I don't know how to checkmate him with at least one queen and a bishop against his bare king and two locked and immobile pawns. I am no GM but few players get to even my level without being capable of checkmating with just a king and queen.
Looking at his rating, a little over 1900 and well above mine, one would think that he would be somewhat less confident. I doubt Magnus could whip me with his position. He must think he can because he hasn't even offered me a draw.
I have faith. If they had a doubling cube like in backgammon, I'd be willing to use it now... and every day for the past two weeks. I know that the only stakes are site rating points but we would be X64 by now. It would be fitting that he go back below 1000 because anybody above 1000 would know the horse is dead.