My cat will play fetch for as long as I throw her little mouse toy. She'll even let me throw it from bed and she'll bring it right back up for me to throw again.
My indoor Devon Rex starts nagging me if we haven't played for a few days or if he suddenly gets in the mood for it. He adores playing for several minutes at a time, until he gets annoyed because he thinks I should know to play with more than one toy at a time. Or that we played yesterday and that I'm stupid for suggesting playing something without his asking for it.
He might have gotten a bit spoiled at some point, I thing.