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 check...
Will your fiber survive the storm?
January 18, 2016
Is after-installation fiber damage acceptable?
Ready to connect to long distance carriers?
How often do you check your lines with an OTDR once they're in service?
Do you test incoming cable on the reel?
Is the sheave the right diameter?
February 2016 (3)
January 2016 (3)