Our elder two cats are 15, one is still behaving like a youngster (although she has always been the poorly one - no teeth now) and the other is just growing old. She's short haired, and her hind quarters have been getting matted/luggy. She tends to spend most of the day sleeping in her basket. She is eating well, still goes out, but only when she wants. The matted fur we think is down to her curling up to sleep too much, and not grooming, so we've spent considerable time this week slowly pulling the matted bits out and brushing her. It can also be an indication of poor health, but so far she's perfectly happy. Again, we are preparing ourselves and just keeping an eye on her.