Hi Tom and welcome to Pet Talk.

My cats since mine tend to live up tp 18-19 years. I live in an apartment in a city so mine are indoor cats only, perhaps yuor situation is different. These are a few things that I observed:

In later years, espcially my male Gigio, developed some kidney failure. So watch out for signs of kidney disease. My cats were no longer able to eat big meals, they tended to want little quantities more often (with younger cats in the house as well this did not prove to be an easy task). Bigger quantities of food would make them vomit quite often. Obviously this might not apply to all cats.

Their nails seem to be less retractable as they get older so I had to trim them more often. I did not want them to get caught in something and get hurt. Gigio's bones also got quite lighter and sometimes he was a bit stiff. He was quite a playful and lively cat up to a month before he left me.