Currently in the game, animals continue to grow up to a certain age after they reach maturity
With the tortoises it’s very old as close to a hundred in the Galapagos and over it with Aldabras, and I’m uncertain if it’s actually too much or not.
With salties, it’s 80 years old, which is actually far too old, as they get near their final size at 20 and finish growing at 50 in real life (though I am fairly certain that the maximum size is still too small).
Either way, the reptiles don’t continue to grow their entire lives in real life, but instead finish at a certain age which is sometimes old when compared to mammals and birds.