I think you should invite Sarah over to visit Max before he has to go. It will be easier for her to understand if she can see that he's not living his best life.

I have an almost-20-year-old Jack Russell who now has a gray muzzle and has cataracts and is losing her hearing. But she still chases squirrels (sometimes she finds out its the cat when she gets close) and can do what she always did. It's going to be hard when she goes. I feel for you.

Karen