A big part about metal roofs and how the fasteners work (and quality of them,, like all things there are GOOD brands and cheap china junk now on metal roof screws, not to mention NOT all of them are so self tapping, some will drive you NUTS when installing, or need pretty much pre drilled holes to go thru, as to good ones, will make the job easier and last, quality matters in all things)
or last is, how well the installer is with usi8ng them, they cannot be tightened too tight, or you will get failures, , you do Not want to crush the washer, that is what causes them to dry rot and fail!
when done right and of good quality, they will last decades and not need any repairs
unless MAYBE some may need to be re tightened as wood will shrink and expand at times,
but again, a good installer will torque them to the right amount which allsows for that!