The death of an amplifier


When an amplifier finally passes away what is usually the cause for it's demise? Can this be prevented? I'm looking to do some preventative maintenence. HELP!
128x128nrchy
I generally try to hose down my system with a pressure washer at least once a week. Should I stop doing that?
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Well Nrchy you can get away with it on the 4th thursday of every month as long as it is an odd day- I know it its tricky but stick with it and it will make sense ;) ~Tim