As Genghis has well explained, there are many safety margins built in to GA airplane structure. Slower than Va, you'd have to massively abuse an airworthy airplane to break it. Indeed, the "break" will generally be a "bend" so far, that once landed, the aircraft is obviously unairworthy. I am aware of three aircraft in which this has been the case - massively abusive flying, the aircraft was landed safely, but scrap afterword.
I had occasion to be involved in the "repair" of a Cessna 206, in which a careless installation on the wing resulted in a drill hole being made into the critical area of the wing spar (right in the wing strut attach area). After analysis, I determined that the wing remained airworthy without a repair being accomplished. I hired a structural Engineer to make a formal determination. The result was that with the drill hole damage, the wing had a predicted fatigue life exceeding 1.17 million flight hours - many orders of magnitude beyond what it could ever fly.
This, of course, presupposes that the airplane is maintained in an airworthy condition. The failure of the aforementioned PA-28 wing was in large part the result of the wing being unairworthy. This would have been very difficult to detect though (it's not an easy area to inspect). This was not the first instance of such a failure in a PA-28 wing, and in the late '80's, I was involved in AD required inspections for the same airworthiness concern. I expect that the newly developed inspection technique will become a means by which the airworthiness of a PA-28 series airplane can be assured.
In the mean time, it's your job as the pilot to conduct the prescribed preflight inspection, and thereafter, to operate the aircraft within its limitations, and with appropriate technique. As said, BRS will be of little use through a lot of the flight envelope in which a training aircraft normally operates, and also introduces other expenses, and reductions in safety. Just fly airworthy airplanes as they were designed to be flown, and otherwise, don't worry about it.