Boney old cat.

I've got a boney old cat. He wasn't always old. When he was a kitten they bottlefed him, with the result that he has maintained a lot of kittenesque qualities for a long time now.
But he's old. About 20 to be exact. Over the past 6 months or so he's been getting skinnier and skinnier, slower and slower, sleepier and sleepier. He used to like sitting on the edge of the tub, but the other day he slipped and fell in. Today he tried to jump up on the counter and missed. His cat-like grace is gone. Given way to geriatric creaks and wobbles and stumbles. He sleeps more than anything else.
We took him to the vet, and they told us it's kidney trouble with him. He's not in any pain. He's just hungry and thirsty a lot of the time. Nothing we can do really, except feed him some more easily digested foods, keep him well watered. At this point he's getting less and less nutrition every day, because his kidneys are starting to fail.
Janet and I both want him to make it through the summer. All of our cats are inside cats, but he loves being outside. Like me he just wants to sit in the sun all day.
We're at the point though where it is a matter of hoping he makes it. We can't imagine him surviving until next winter. He may make it until fall... Summer isn't even a sure thing even.
At home we sit with him on our laps a lot, me and Mommy and the kids. We're giving him all the time we can, and he purrs when he sits with us still. Janet bought him a pillow to sleep on, and while the days and evenings are still cool, he sleeps there. Summer should be here soon, and then he can lay in the sun again.