I have a 9-year-old cat that has been with me for 8 years. He was a stray at a shelter when I got him and he is somewhat socially dysfunctional. Recently he has started to hiss when I play with him. He doesn't hiss at me but at the ribbon I use to play with him or the pillow that he knocked over while playing... The ribbon is a new toy and both cats enjoy it. His behavior hasn't changed in other ways so I'm not really concerned. I'm just curious. Is he getting too intense and should I stop playing with him when he hisses or play with him until he is tired? I lean more towards letting him wear himself out. At 9 years old it doesn't take that long.