Why dust is the Tiruppur problem
Every town has its own dominant fault, and here it is thermal. Airborne fibre finds its way through the intake and settles in the heatsink, where it forms a mat that air cannot pass through. The processor protects itself by slowing down, and the machine feels like it has aged three years in a month.
The fix is not expensive. Stripping, cleaning and repasting brings most machines back to their original speed. What makes it expensive is leaving it, because sustained heat is what eventually kills the board.
If your laptop lives near a production floor, a clean once a year is worth more than any upgrade you could buy for the same money.