I'm looking forward to replacing screws for a living when I'm 50 years old. We just replaced a 10 year old metal roof on a garage. Leaks caused purlins to rot all over the place.
There is another building up town owned by the bank. They called me after they had a very prominent Contractor in town put a metal roof on half of the gabled building. He didn't install ridge cap so water is funneling down it rotting the purlins, I'm sure. I told them, they did nothing.