I agree re; vacuuming. I think the extreme cold and the moisture induced from a can does FAR more harm. I hold the end of the Hoover close and gently brush with an old soft 1/2 incher, Job done.
(Cleaning out boy, cleaning out. Dirty minds 
)! Never blown a board by cleaning or adding/removing cards. (
So far......).
Regarding OP; How hot is the power supply upon shut down as start up uses far more power than steady state running. Just a thought.
The REAL cure of course...... never switch it off, just leave it running!
