Does thermal paste age well? I wonder how much if that was bad initial application vs the ravages if time.

AMD gave us a dual socket test system (back in the Phenom days) which started failing after a couple of years of very heavy use for builds, CI, etc. After much head scratching I eventually found that the thermal paste had dried out, and simply reattaching the CPU fans with new paste fixed the system and it lived for quite a few more years after that.

That is excellent advice. I've had machines that started out pretty quiet but got noisier as they got older. I figured it was gunk accumulating on the fans or other parts, but I guess checking the paste is a good idea too.

It probably depends on the type of paste, but I've found completely dried out paste in old systems that would just fall into pieces when you touch it.

depends on the paste, but safe to say 10 years is probably beyond the duty cycle. its $10 for a tube of arctic silver (I went with Arctic's organic, non conductive one I forget the name) that you can use for 10 or more applications. it takes 5 minutes to replace the thermal paste on a cpu.

remember intel cpus will simply throttle themselves at high temps, so replacing the paste will allow heat dissipation across all the cores (as I witnessed first hand)