Whats the average i can expect my Tri-colored Milksnake to live? I would guess he is around 10 years old. I got him as an adult about 8 years ago. He seems to be a bit lethargic and slimming down now. Could that be a sign of him showing his age?

I have never bred him or had him with another snake. He has gone off feeding before in the past but never lost weight like i am noticing now. He did eat last week and his feces looks normal as it always has.