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.
I've seen other comments pointing their cats only doing it when kittens, but I am happy to report that my 3 and a half year old boy does still play it. I throw aluminium foil balls and he loves playing soccer with them and giving them back to me so I can throw them again
