I help collect donations for a local shelter and as soon as puppies go on for adoption they are snapped up. It breaks my heart for the oldies who seem to have been there forever, especially the ones who their owner has died as their whole world is just turned upside down.
They have a separate part for the really old ones and ones that have really bad health problems that can't be rehomed. They have sofas and beds to lie on, a real home from home, well as near as they possibly can have.
I find older dogs are a joy, they seem more settled and just want cuddles. The pain of losing a dog is awful, they are your family, but to give another a wee chance is a lovely thing to do. I have never gotten over the death of my last dog, she was a sweetheart, but my rescue now has helped me just as much as I've helped her.