I didn't know they needed "cleaning".
It's too bad that OS' weren't more wise to this. Right now there are certainly millions of desktops and laptops that are running far below their potential because it is forced to thermally throttle, yet there is no indication for the user beyond things being slower than it once was.
In-laws were going to throw away their computer, random freezes in the summer. Needed a thorough clean, "good as new".
PC World/Microsoft lost a sale though.
The OS does see the perpetually fluctuating frequency state of the processor, though, and can monitor it over time in a correlation with the temperature and display a simple aggregate performance metric, flagging as a system alert when performance falls below a set threshold. I've had relatives whose system saw a dramatic, very noticeable usability improvement after a couple of quick bursts of compressed air.
And the performance impact can be absolutely extraordinary. I've seen systems go from barely functional to completely decent via a simply cleaning. Note that there were no faults or errors in the former case, it simply was forced into perpetual thermal throttling. In modern processors this case halve and worse your performance with ease.
I'm really surprised people don't figure out to clean their laptop organically, I figured it out myself - after about a year of daily use of every laptop I've ever had the performance degrades very noticably, it becomes hot to the touch, and the fans spin to the max. I've even had shutoffs due to overheating. It just seemed obvious to try to dust it out to see if it cools it down. It does.