Regarding Filou I think the fluids are not a lot of stress. And the life he is having is a fun life. Yesterday a moth came into our living room and he had a ball catching it (and eating it )
He is happy, cuddly, funny and sweet. I feel I'm doing the right thing for him. If you feel Cosmo doesn't enjoy his life- then you may question it. But on the other hand if he's happy- then he should get his fluids as long as they help him.