@Markmac - @turn them off... -
>> Yes, that would be those of us who measure MTBF for monitors,
>> HDDs and cheap retail routers.
MTBF is measured in hours on – so if the period off is a greater percentage than the reduction in MTBF for the power cycles you gain life by turning it off.
The only research I have been able to track down on subject suggested break even point was 8 – 12 hours a day
Of course since you say you measure this sort of thing – you can point out some better evidence on the web covering life expectancy and powered on/off duty cycles
>> You may not have experienced this but in the last few years I've seen all of these
>> fail due to mechanical stress as a result of heat/cool cycles.
Helped someone sort out PC when they believed it was heat/cycle issues – heat was right, the HDD had been cooked by in-adequate ventilation and the case vents were clogged with dust through leaving it on 24/7.
Similarly I have found cheap PSUs working at close to maximum spec – as typically found in routers and set top boxes – die whether on 24/7 or not – replaced with a quality PSU/one working under spec – they go on for ever – conclusion they aren't correctly spec'd to for the expected duty cycle loads (i.e. they can deliver the load for the short periods or deliver a lower load for long periods). And strangely usually the warranty replacement PSU plug/block is very different from the original one