The bags will hold up as long as you want to age. They adhere to the surface of the meat and form a bond, so that doesn't change. According to the website, the best cuts to age are the subprimal cuts; ribeye, strip steak, and top sirloin. There are differing opinions on length (probably driven by taste) between 14, 21 and 28 days. I've aged prime rib for 8-9 days in the past, so this is my first 21-day adventure!
Here's a shot of the steaks prepped with onion salt and Jim Baldridge's Secret Seasoning, and warming to room temp!