How do you know it's time to replace Recoil buffers and springs?

[WHG]

I've got a Colt H-Bar that I purchased new about 17 years ago. I've fired over 20,000 with it. I was just wondering if buffers ever wear out, and if they do how do you tell they need to be replaced? I would think the spring should be replaced a some point also. The rifle functions just fine right now, I'm just trying to prevent a problem from developing. The rifle has a standard non-adjustable stock.

[joem]

I'd call Colt and ask for the length of the spring, then measure yours. Other than that I believe you would need a device to measure the resistance of the spring in pounds.