After 14 to 21 days of hanging, the only thing that happens after that is that you start to lose a lot of rail weight, which then decreases the value if you are charging a fixed per lb/side amount. That's usually why producers will not go beyond 21 days. My family used to go 21 to 28 days on the rail of Alberta Beef. After that, select primals would be hung further, but that was for our own consumption, and we liked the more intense flavor you get from losing more intramuscular water. Beyond the 28 day mark, it does start to look quite a bit more like rotting meat though.
