My cats are both quite young. Snookie is five, and Minnie is two and a half. Minnie lives upto her name and is tiny, and thinks she's a kitten though. Neither really affects the household - they are both in good health and don't require a lot of "work". I think we have become immune to hearing Minnies bell as she zooms around the house though.
My friend had a cat who lived to age 20 and passed away a few months ago. Even though he was very old, I don't think they really needed to do any special care for him either. Some things you may need to consider for an older cat are switching to a soft food, and considering physical challenges such as walking up the stairs and maybe moving their bed and food bowls downstairs.
