A roof doesn’t exist in a vacuum so may be victim to falling branches, destructive humans, high winds, lightning or shifting of the structure, all of which may cause leaks. If you absolutely can’t have water hit the inside of the building then make sure there is a secondary layer of waterproofing under the roof. If you don’t want a secondary layer and just really don’t want leaks then:
Clear away all branches/trees from the sides of the building
Limit human traffic on the roof or at least unattended human traffic
Make sure the roof is inspected initially by the manufacturer
Have the roof inspected periodically and after any storm by someone with sharp eyes, roofing knowledge and patience.
THE BEST WAY TO EXTEND THE LIFE OF THE ROOF IS TO FIND AND FIX ALL PROBLEMS EVERY SPRING AND FALL!
