And a part of me feels horrible for replacing Tristan before he's even gone.

Well... if you needed a defense, let me try this out. When Skitty was dying, if someone had been able to give me something to do - not even necessarily for a cat - it would have been a great kindness, because I hated how helpless I was. And if I could have dedicated that help to Skitty, after a fashion, it would have been so much better than just not doing *anything*.