This goes back to the very start of having a personal computer.
Back in time, microsoft always said to clean.
For a while, HP and Dell would have a special note in the box of new computers telling you to clean the inside, and instructions on how to do this.
Everyone should clean every 6 months.
One reason I have my CPU off the floor (that way, no carpet lint, dust, etc from the floor).
Does help to keep it a bit cleaner.
Another is that I put a coffee filter (hey it works! and cheaper than anything else out there) over the intakes.