Is this a load of rubbish, or is there a genuine reason why they have to stay on? Will they lose their settings if turned off?
That's rubbish. Been using our for about 4 years and it gets switched off regularly with no ill effects whatsoever.
If they are v2 ones (i.e. black hockey puck type and older than 12 months) look after then as, although they cost about £70 each new, they sell for about £200 now as they're the only ones that can be jailbroken to run additional software - such as XBMC. Makes them much more desireable.