equipment failure is always a pain in the ass. i usually have two amps and two guitars, cuz u never know. have a regular service BEFORE amp breaks down is really good as well. Dont wait till something goes wrong. form time to time i open up my amp to the max and play it for some time just to see if everything is still ok. I once read that van hallen use to lave his guitar next to full open amp in feed back for few days. if he came up and the amp was still working, it worked :) haha