How will you know if the airframe has been over-stressed? Almost certainly it will have been if is 30 years old. Gusts and hamfisedtness will pretty much guarantee it!
With a monocoupe structure you might see some deflection - the pre-flight 'walk around' is not supposed to be window dressing. With a pin jointed type structure - Pa18,20,22 and many others it is possible to damage the bolts and so the walk around needs to look at these joints - particularly looking for any witness marks.
But realistically unless the structure isvisibly deflected most pilots will not notice. But light aircraft do not fall out of the sky very frequently -and that tells you alot about the design code reserves of strength and maintenance.