Leave solid state amps on? Or turn off everytime?

I will raise this point again, partly as I don't know the answer. Ask a fireman in the UK the commonest cause of house fires, it is TV's left on standby. In theory then, electrical equipment on standby, is a fire risk. I have never heard of a fire from this cause, has anyone else?
As an aside, I am not convinced that most equipment takes more than half an hour to get to optimum performance, at least mine does'nt.

there seems to be 3 questions here that are getting confused.
The question of the ethics of leaving kit on all the time, in terms of global warming, use of finite fossil fuels, etc etc. Now I am in the camp that says you should take cognisance of that, but I am not lecturing anyone else on this.
Second, does it make a real audible difference? For most kit, is performance really degraded in turn on? I have to say, I am not convinced, but that is just me and my setup.
Third, does kit last longer left on or switched on and Off? As someone else said, I am not qualified to comment, but I suspect it differs from amp to amp