Clean your PS3 for dust every month. You get all the dust out of it, the smoother the PS3 runs and won't overheat.
It does not have to be done monthly unless you life in a dust bowl. The best way to clean a gaming console is to take it apart and clean all the dust and crude out of it. Its a PITA to do this monthly. At the most Id clean it out every six months to a year or yearly after the warranty is out.