We are in exactly the same situation with our 20 year old Mamma Kitty. She neverr was a big fan of using the litter box in the first place, but now the free range peeing is getting really bad. But...
She seems happier than she ever has been in her life! The other kitties seem to know that something is up with her, and they are extra lovey dovey with her and she seems to be enjoying that in spite of the fact that she had never been a cat-social kind of ca before. The weather has been nice, so we've been able to corral her in the front yard, and she's really enjoying that too, since she started out as a feral, outdoor kitty who didn't like having to stay inside.

a couple of times, on her bad days, I found myself thinking that it was time for the last trip to the vet, and she suddenly sat straight up from a dead sleep, made eye contact and began to purr like I've never heard before. Clearly she doesn't think it's time. I have to confess that I have moments of resenting the mess she's making of the house, but I sure couldn't look into those intelligent eyes, knowing that she wants to live, and have her put to death. It's a really tough choice. and it really sucks.