Question When shall I clean the surface of the i9-9900K and apply new thermal paste?

[modeonoff]

Hi, I built my PC four years ago. When is a good time to replace the thermal paste? If I don't do anything, will the thermal paste dry out and shorten the life of the CPU?

 

[SkyNetRising]

When is a good time to replace the thermal paste?

When you experience issues with cpu temperature.
If temperature is fine, then there's no reason for repasting.