at a certain size or age do they lose it?
16 year old Dovii is very old. Do you have a pic of him.
My old JD and GT females stopped laying eggs after 2 to 3 years of active breeding. It appears that they have a finite number eggs to lay and once gone, they are done breeding. I don't know about male though because the females were done before the male. The male got mean to the female when she refused to cooperate.