Just because your cat is old doesn't mean she is all used up! She may have fewer years left to play and purr and keep you company, but she may still enjoy all the things she always did. The key is to keep her happy and healthy. And you need to be more attentive to her needs as her body changes with the aging process.
As with humans, cats can experience hearing loss, decreased eyesight, cataracts, arthritis, diabetes, heart problems, digestive problems, and a general slowing down of all physical processes. While she may still play and chase a string or a ball, she may not do so as often or as vigorously.
But with proper diet, appropriate exercise and a happy, stress-free environment (preferably indoors), many cats can live more than 20 years. (By contrast, outdoor cats are lucky to make it to their second birthday.)
If kitty develops joint pain, usually due to arthritis, she may feel less inclined to play, or even to move around, and may nap most of the day. If this is due to pain, she will decline faster from inactivity, losing muscle mass, making further movement more and more difficult.
A good massage feels great at any age, although youngsters may not appreciate a session. As we all age, sometimes a relaxing massage is just what one needs to keep the old bones a-movin' so we can get through another day. It takes a special touch and the right approach to massage a cat, since we can't explain to them what we plan to do. Learn how it's done with the information here:
Cat Massage Secrets
The bottom line with any pet's well-being, including their old age needs, is the concept of consideration. When you grow old, won't it be nice if your family is considerate of your new needs? Just do the same for Fluffy, and she will appreciate you for it.