An old roommate of mine had a Huffy road bike with the same dropout attachment. It was fine enough when he got it, 20 or so years into its life, and was still okay when it was inexplicably stolen from our West Philadelphia apartment building's porch with the aid of a tree branch in its cable lock.

FWIW, the only bicycle frame I've ever broken (that I'm aware of) was a 1978 Schwinn Varsity that started squeaking not long after I got it ~ 2003. The non-drive side derailleur hanger had actually sheared within the "arms" of the hanger.