I left a Cello Duet 350 powered on for most of eight years -- only took it down for vacations, renovations, cable changes, etc. Bought it in 1992. Now it runs in my home theater and is powered up only when the system is active (maybe 4 hours a week) -- but it certainly suffered no ill effects. One caveat is that electrolytics have a rated life -- so they will age more quickly if the amp is left on; the semiconductors, it seems to me, benefit from being left on (fewer transients and fewer temp changes). Since the amp is now nine years old, its capacitors should be replaced. I used to manage service for $5-15 million (per copy) mainframe computers -- and the absolute worst thing that customers could do was to power them up and down -- the process inevitably shook out the weak components. A machine that had been powered up for months, once powered down, was a good bet NOT to come back up without some expensive repairs. Those experiences have always left me convinced that electronics (w/o moving parts) are probably more reliable if left on.
Solid state power amps.; on or off?
Some people keep telling me that solid state gear should be left powered on all the time during day to day listening. They claim that thermal consistency will improve long term life and reliability. Power cost consideration appart, what is your opinion; experience?