But I don't know whether to change it or not
Coolers don't go bad. It is just a hunk of metal. Assuming it properly cooled your CPU when new, If the fan is still spinning properly, and the cured bond of the TIM (thermal interface material) has not been broken, there's no need to do anything. Just make sure the case interior (and heatsink fan assembly) is clean of heat trapping dust.
Remember, it is the case's responsibility to provide an adequate supply of cool air flowing through the case. The CPU cooler need only toss the CPU's heat into that flow.
Also, there is no need to replace TIM just because X amount of time has passed.
Only if the cured bond is broken do you need to replace it. There is
not one TIM maker, CPU maker, GPU maker, cooler maker, PC maker, or motherboard maker who says TIM needs to be replaced periodically.
Not one! TIM will easily last 10, 15 years or longer - AS LONG AS the cured bond is not broken (through abuse or, ironically, twisting to see if broken!
).
If you "
need" the extra few degrees a fresh application of TIM
might provide to prevent instability or thermal protection features from kicking in, you have much greater problems than aging TIM and they need to be addressed first. These include dust build up, failing or inadequate case cooling, or improper overclocking.
Remember too, the purpose of TIM is to fill the microscopic pits and valleys in the mating surfaces between the CPU and heatsink to prevent insulating air from getting in. Even if the TIM dries, the solids left behind are still doing their job of keeping that insulating air out. It does not need to be replaced if dry. Note the only reason TIM comes in liquified form is so it can be squeezed out of the tube and spread evenly across the CPU die.
There is greater risk of damaging the CPU, pins or socket through mishandling or ESD than from over heating, again, AS LONG AS the cured bond remains intact.
