Manuals never say to leave on, but some people do, and it is common praactice in the professional audio industry. I first experienced the idea at a sound dealer who left their solid state Mcintosh power amp on all the time. Some feel it actually extends rather than shortens component life just so long as it's a component that won't generate alot of heat at idle. True there is no need to leave on, but amps usually sound better after being on awhile (unlike "break in", the matter of "warm up" is well accepted, amps just sound better warm or hot than from cold, when you turn it on it is cold and will raise temp as it plays). I leave mine on and I use the mute switch when not playing. Anyway you might try leaving it on for 24 hours, then turn off, this will allow the power supply capacitors to fully discharge. Try it a few times over a one week period. After that either leave on or turn on only when in use. Both the matter of component break in and leaving gear on is often debated. Poke around on the net and I'm sure you'll find plenty of opinions. My cd player positively sounds better after being on for a few hours, so rather than wait, I leave it on all the time too.