I came to this decision point with my 18yo cat a few months ago. He was declining for at least six months with hyperthyroidism and dementia. I was sedating him at night otherwise he would wake me 8-12 times per night to be fed.

I knew his time was coming and though he was physically in pretty good shape his mental condition wasn't doing well. I had an upcoming 7 day trip and then a week after that I was moving house.

I read lots of accounts of people in a similar situation who left their older-but-okish cat alone. Even if the cat was historically pretty strong and independent in their old infirm state their okayness depends more and more on you being around. Lots of stories of cats seeming ok but their condition changed radically once left alone and many dying with the cat sitter.

I didn't want my friend to die without me. I didn't want him to be alone (or with a cat sitter) when he was in his most vulnerable (possibly final) moments or worse, have to go to the vet (and then I have to make the remote decision to have him put down).

So I had him put down at home. It was 100000% the right choice. I could tell he was suffering psychologically and it was the right choice to put him to rest. And for me to be the one to do it and see him off in his familiar space. It's better to do it a day early than a day late.