My cat Jane is 4. She's a runt though, so she still looks about 8 months old. It's interesting when people meet her for the first time, because they often think she's much younger than she is. I've had to bust out her adoption papers to prove her age before!
She's definitely quite active and spry. Though she's a champion marathon napper, she'll do sprint circuits of the house for hours when the mood strikes her. She also recently learned how to catch and eat bugs. Before that, she would just follow them around, watching them. Once, she got her nose really close to one, it touched her nose, and she jumped backward in terror. It was hilarious.
I think her age affects us in that she is very curious, but skittish when faced with new experiences. I feel like an older cat would be a bit more blase about some of the things that send her into a tizzy. She also needs lots of reassurance from me that she's safe, sort of like a kitten. I don't know if that one is an age thing, or if she just has a nervous disposition
