I see this often. It is rare for people to take the side panel of a desktop to clean a system and even rarer for a laptop.
In some instances, a system with a large and well ventilated case can run ‘dusty’ without problems, however, the more compact your system the more severe the effect of dust. As such I have found that slimline (low profile) desktop systems are very prone to overheating as they age. Laptop tend to be well protected and it is harder for them to get dust contamination but it does happen.
In short, if your system fans start to speed up and the PC becomes erratic, hanging or crashing, it may well be due to overheating issue caused by dust clogging the air flow.
Here’s a few images of a low profile Dell system that I have recently repaired for a client. It was noisy (fans) and the system would hang or crash.
A physical clean up of the system by removing the covers and using a soft brush and a gentle vacuum fixed the problem. This saved the client hundreds of pounds as they were ready to purchase a new system!!