how long do people usually live after a kidney transplant?

hey guys :) my girlfriend had a kidney transplant when she was about 12-13, and she mentioned something about probably not outliving her parents and it just made me wonder what is the average life expectancy post transplant? i know they “expire” after 8-10 years but i thought you could get another one (obviously i know it’s not that simple to acquire a kidney but just for arguments sake lol) and have it for 8-10 years again. any help or information is appreciated, thanks everyone!!