Hi Bud, There are of course two schools of thought on this subject and it also depends on the equipment. The biggest strain on the components in an electronic system, usually takes place at 'Switch On' and many failures occur at this time. If the majority of the circuits are solid state then provided they have adequate ventilation, they should not really wear out when left powered up. It was a bit different in the old valve days(Tubes to you in USA) , since they slowly deteriorated all the time they were powered up. Most of the electronic equipment in my home workshop and music studio is left switched on 24/7 including my desktop PC. The only things which I switch off, are items which I don't use very often and those that consume a lot of power. Also, all the PCs at my workplace are left switched on 24/7.
Items such as sound mixers, CD and cassette players don't consume much power so shouldn't contribute a great deal to the average power bill. I don't imagine the projector is left fully powered up - that would certainly bump up the electricity bill!
The lamp is of course the most vulnerable component in a projector but some makes incorporate a surge limiting device which protects the lamp during power up.
No doubt, you will receive some more views on this subject.


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Willum