Seems straightforward - but on notebook systems which most people never take apart you don't really notice the dust buildup. The fans typically are very close to the outside environment, therefore dust can buildup quickly in the heatsink fins - this affects both passive and active notebook cooling by a HUGE margin.
As an example, I just cleaned out mine by blowing compressed air through the fan vents, and my temps for both CPU & GPU went down by nearly 25C. (I hadn't done this in a year)
My CPU fan was constantly turning on, and the GPU was overheating & throttling during gaming. For some reason I thought that scorching undersides and 90C was normal for a laptop GPU... now It struggles to get above 71 degrees when I overclock it...
Key Recommendation - Dust out your fans!
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