Interesting about fatigue.
My personal aeroplane is subject to an Airworthiness Directive whereby a spar strap is required to be fitted at 5500 hours airframe (fortunately, quite a long time off as I purchased a very low time example), and indeed a similar type from the same manufacturer had a 'nearly' failed forward wing spar, the source of which was a manufacturing defect.
So, even though your airplane is looked after properly, problems can be found...fortunately most times early enough to prevent smokin' holes.
Composite or wood airplanes are much less affected by fatigue.
With regard to composite structures, this remains to be seen.
Aluminum aeroplanes have been around a very long time, composite ones much less so.