CPU cooling: How often do you need to apply thermal paste?

Thermal paste is used to glue the heatsink in place. You don't need to apply it at all unless you're changing them.


EDIT:


I didn't say that it was a glue. To the person who can't read, below. Indeed the CPU is held in place by clips, but what then holds the heatsink in place?CPU cooling: How often do you need to apply thermal paste?
Anytime you change the CPU or the heatsink attached to it basically.CPU cooling: How often do you need to apply thermal paste?
Thermal paste should only be applied when you fit a cpu or fit a heatsink to it. It should only be a tiny blob, match-head size or so, should out thinly and evenly. It isn't a ';glue'; at all, the previous answer is incorrect. The cpu is held in place by clamps, it is only to ensure there is contact between the cpu and the heatsink, to allow heat to be conducted away from the cpu.