What is approximately the life expand of a cat?

my cat had always been very sweet and lovable. lately she gets aggressive an start sniffing and bites herself in the back if i try to hold her she wont let me and she starts sniffing and bitting herself and she gets pretty ugly. why is this behavior. she never did any of this stuff. some friends told me it is because she is too old. she is about 9 to 10 years. always lived inside, eats well, she lost most of her teeth, and has some bald spots on her. is this a sign of her deteriorating and approaching death. please let me know.

Well, the average life expectancy for an indoor cat is usually considered 12-15 years. Of course it is not unusual for a cat to live into their late teens and even 20's is not unheard of - especially if they are well cared for. Genetics also plays a role. Some breeds (such as Siamese) are known for being exceptionally long-lived. Genetics can work against you too though - My Rainbow Bridge cat Moose died very suddenly at age 7 of HCM (hypertrophic cardiomyopathy). Bottom line - just love your cat and enjoy the time you have together.
My 3 cats that have passed away made it to 18, 19 and 21 so you've probably got a good few years left with your cat.

TAKE HER TO A VET!!!!!! Why has her behavior changed? Why has she lost most of her teeth? And, why does she have some bald spots on her? PLEASE take this cat to a good vet!!!!!!!

TO: THE ANONYMOUS USER WHO ASKED THIS QUESTION; PLEASE READ THIS!!! I know it has been over 6 months since you have asked this question, and you have probably tooken her to a vet by now and found out what was wrong, but I am a huge animal lover and have had 8 pets: 3 boxer dogs when I was still a baby. my parents sold them before I was even two years old but ive seen pics of them. A cat, sylvester, who I had since I was two but has been missing since april 2010. A dog named max who I got when I was one but died when I was three. Another dog, Chloe, who I got when I was 3 but died when I was 9. A dog named Socks who was seventeen yrs old when it died last summer. And my only alive pet today, Speckals, a cat. I hate it when animals die. But I would really like to know what was wrong with your cat and if she survived. Please comment back and tell me as soon as you read this. Thank you so much!