How will I know if my dental bonding is going to fall off?

I got dental bonding about 13 years ago on my front tooth. I had a calcium deposit and I believe they shaved some of my tooth away and then put the dental bonding on. The bonding is still completely intact however I read they typically only last 4-8 years. I'm terrified of it just falling off one day. Are there signs when its nearing the end? I would like to know how to determine if it is okay or not. Also would it only fall off or do they also thin or wear away over time?