Depends on a number of things. Firstly, there's unpainted, possibly harmful UV rays working against longevity. Can't say for sure urethane clear really helps either.

But going back to the early monocoque Kestrel. They were heavier but remarkably strong and could handle hard hits. You could take chunks out of it and they'd be just fine. I only know from years of beating up an early CS-X 'hard tail' mountain bike. Also quite sure most steel frames would have been severely damaged on a few experienced endo's and frame slams.