Well overhand shots will "beat up" a disc faster due to the way it hits the ground (basically vertical) so your trak is going to become more understable and flip easier if you keep throwing it overhand. But these disc are durable and can take a lot of abuse.
Basically any disc you throw overhand constantly it will beat in a little quicker. I'm with you on the specialty disc, all my disc are rubber and my bag is a double nutsac, even in a tournament I only my nutsac. I just use a couple of disc, then the rest of my bag is just back-up. No need for 25+ bag in my eyes, unless you are doper worried about water