I also know a lady who bred some dogs from Stratton dogs, namely off a bitch she called Rip. The ones I saw didn't take 30 minutes to come unglued, and they were off the Dio Duel/Rip breeding.

In regards to mouth, it is another trait. If you want to successfully have that, then you have to breed dogs that have that trait ALONG with whatever else it is you want.

I agree also that hard biting dogs that "try their hardest" to do anything "all the time" will blow out sooner than others as they're putting themselves in a position to quit. The only drawback to that is if that dog is able to get where it wants and utilize what it has, but that goes for pretty much anything.