That seems to be how older snakes go, though. They just slow down and pass without much fuss. I'm sorry for your loss. If it makes you feel any better, she had a nice, stress-free life with you. In the wild, her chances of surviving even one year are very slim, and then she would have predators, parasites- heat, cold- even the stress of reproduction. With you, she had nothing to worry about for many, many years. The fact that she lived so long is testament to your good care.