I still have a DLP rear projection set that I am using...the excellent LED driven Samsung HL61A750. I have had the set almost 5 years now, and have put almost 20,000 hours on it, according to the timer in the service menu. Well, last Sunday, entropy finally caught up to the set, and I got a large error message across the screen..."Check Fan 3". Uh oh!
I grabbed a screwdriver and pulled off the back panel...and was greeted by a layer of dust so thick, it had totally filled in the gaps in a heat sink! I took the set out to the front porch and took my air compressor to it...CHUNKS of dust few out from various nooks and crannies, and from the blades of the three internal fans. 5 years of accumulated dust was purged all at once...it was astounding how much was in there! After I cleaned it all thoroughly, I buttoned the set back up, and everything is working fine once more...I may get another year or two out of the set, hopefully!
The moral of my story is that you should regularly clean any electronics and get rid of accumulated dust. It clogs fans and heat sinks, causing your equipment to run MUCH hotter, and will shorten the life of your gear! This goes DOUBLE for electronics that use fans, as they will pull more dust through them, where it gets trapped! If you don't have an air compressor, you can get "canned air" at most electronics or computer stores.
I would only recommend doing this yourself if the unit you are cleaning is out of warranty. Also, be VERY careful not to stick your fingers where they shouldn't be! Touching a large capacitor or parts of certain power supplies can ruin your whole day! That being said, if you are careful, it's a trivially easy job to perform and it will save you thousands of dollars replacing gear that could have been saved with a little care and maintenance!