Don't keep it to computers/laptops..

All electronc devices, ham radio transceivers, PSU's P.A.'s satellite recievers etc.

Takes me 2x a year 1/2 a day to clean the stuff out, and cause massive duststorms in the back garden...

Anything with a fan, clean 2 x a year minimum.
Anything without a fan, clean out 1 x a year.