Please describe exactly what you mean. Are you referring to how long and when they are able to produce viable eggs? Or are you referring to how many years they are reproductively viable?

My female was born in 2003 and laid a clutch consisting of 13 fertile good eggs this year and maintained great body weight. 10 years of reliable reproduction I would (guess) be average for females, longer for males. The early spring copulations (late Fed - late March) seem to the most critical in terms of reproductive success.