This debate has been bugging me from the very beginning. For answers I put all possibilities plus an other category for the possibility only certain models within each group age, or the writers have something weird up their sleeve, always a possibility.
I firmly believe that all models age. I have used Tigh as an example in other threads, which means the final five must age. As for the other seven, I think the final five made them in their image and followed suit. As for why it hasn't come up yet in the show, its only been a couple of years and the models who have not died and been resurrected into fresh bodies have not had time to noticably age. Thats why the actors who played them, who have aged, still look almost the same as they did when they were introduced.