I agree with Bebop - I switch off everything (PC, Recording equipment, PR900 piano, Sound Module, KN6500)and this is on the advice of my brother who is in the jukebox business. Not only does it reduce the fire risk but it also cut my electricity bill by nearly £9 per month.
However, all this equipment uses individual electric sockets which are 'Surge' protected.
They are controlled by three 'spurred' switches which are also protected.
I have now used this system for some three years and can honestly say for me it works.
i.e: we had a local power cut recently, causing a complete 'black-out' in the area. It happened about 9.30 pm and fortunately for me, all my equipment was switched off and my equipment wasn't affected. However, my friend admitted he lost quite a bit of computer work he was doing and his PC misbehaved for several days afterwards, so he has now had 'surge' plugs fitted. As the Boy Scout's motto says "Be Prepared"
Hope this helps.
Aud