What are the common signs of wear and tear on overhead garage door springs and when should they be replaced?

Common signs of wear and tear on overhead garage door springs include visible gaps or breaks in the spring, uneven movement of the door, and loud creaking or grinding noises during operation. Springs should be replaced if they show any of these signs or if they are more than 7-9 years old, as they may be at risk of breaking and causing damage or injury.