How often do you clean your PC?

I hoovered the keyboard out on my work laptop (bits of cheese roll blocking the keys), then had to retrieve several keycaps from the hoover bag...

 

in the 80's when I started in the IT industry departmental servers designed to sit in offices used to have filters, problem was that you had to clean the filters regularly. When they started appearing without filters I assumed that they were hoping that most of the dust would be blown out again. A few years later variable temperature controlled fans started appearing, this minimizes the air flow and therefor the amount of dust sucked in.
If one of our customers happened to have some building work going on that would cause problems.
on PC's these days I normally use a vacuum cleaner when you see some unreliability or fans working harder. vac out first, remove boards, vac again, put back together. hope its working better

 

I find also that a sprinkling of Shake'n'Vac really does put the freshness back.

 

I like to use thisas the static picks up the dust without any effort