I can be lazy, and leave mine on for long periods of time.
If you want tangible results try leaving it on for a month, and then try turning it off whenever not in use for a month. I'd imagine the difference will be seen on your hydro bill. Either way I think the answer to the question is moot, there are plenty of guys / gals on this site that have had their equipment for 10+ years and it sitll works fine.
A more likely situation will be that you will suffer a bad case of the upgraditis and buy something new in the next couple of years with your current reciever in good working condition but minus the new baubles you want.
All that said, I'd say turn it off when not in use simply to be energy concious and to save a few cents/dollars on monthly power bills. Be environmentally friendly, cause though the picture on your TV of lush green sceneries is pretty, constantly leaving on any power using source is only contributing to the decay and destruction of it.