I personally don't trust leaving any audio preamp or amp on all the time.If the company that build it says to do so,I'd still pass on the idea.Every piece of audio gear I've listened to(tube or solid state)seems to reach its full potential in a half an hour or so.I imagine you will get a lot of opinions,but for safety reasons I don't like the idea.A lot of class ab amps get fairly warm,depending on the bias and design.Pre-heating sounds like a good option. Things do fail.Just my 2 cents.
