Many issues related to a software or application’s slow performance, extraordinary overheating when gaming etc. is due to the dust bunnies.
If you have a Laptop, this is even more so. Check this excellent write-up on life-hacker, which should motivate you enough to take care of that dust build-up.
For people who do not get respite from plain cleaning, a re-paste job (replacing the heat-sink thermal compound) would do that extra thingy.