How often do you check your lines with an OTDR once they're in service?
Checking at least your unused fibers periodically for attenuation changes can identify signs of future trouble before it gets out of hand. Having said that, those sorts of "creeping" problems are unusual in well-built systems.
Much more importantly, periodic OTDR checks keep your crews familiar with their OTDR, test access locations, as-built network records and any details of particular routes.
The next question: Is after-installation fiber damage acceptable?