Our last old boy finally gave in to time last November, a couple of years after his brother had popped his clogs and left him in peace. He was about 18, so not really unexpected.
It does mean we have a little force of nature in the house now. A few weeks of the place feeling empty drove us to the cat rescue place where we picked up Isla - a tiny 5 year old tortoiseshell who wants inside every cupboard; to sleep on every lap; to chase and fight and basically burn off energy in every way imaginable.
She's seen off the local 'top cat' already, although she and the chickens seem to have come to an uneasy truce. She doesn't get too close to them and therefore they don't chase her.