This happens to me alot, ive been through a set of christophes and just yesterday a nylon. Ive found that my leather straps dont break as easily but when it happens you have little warning, whereas with the nylons i can start to see them fray. This is one of the reasons i run 2 straps, a nylon as my primary near the entrance to the cages and a leather after that.

Not all straps are made the same, the kashimax olympic doubles have a layer of plastic between two layers of leather to increase durability.