Breakers are a mechanical part. These parts have lifespans of 20 years, give or take. See below for a variety of factors can cause Electrical Breakers to go bad.
1. These breakers have been overloaded for to long.
2. The breaker could have a loose connection causing it to over heat.
3. The breaker could have been exposed to water.
4. The breaker could have been installed incorrectly from the begining.
5. The breaker is not the correct type for the electrical panel it is installed in.
Either way when/ if an electrical breaker goes bad there is a reason for it. Stickler's Electrical Service reccomends that when this happens call a Licensed Electrical contractor to come assess the situation. There maybe more to the problem then just the breaker being bad.