A long long time ago at uni art school, one tidbit we learned was to switch off the "emerging new breed" (now every day staples of our creative endeavour) of electronic cameras to prevent unnecessary battery drain and accidental exposure through handling e.g. packing away in its toploader, which is a tight fit and exerts pressure on several buttons, including the shutter. Thus, ever since my much-loved Canon T90 in 1988, I have switched the cameras off at the end of a shooting session, right up through several EOS bodies to the current EOS 1N ('Brutus', running off PDB-E1), in which the lithium batteries have been in service all of 7 years now. Some LCD displays may 'ghost' if left on persistently long enough.

Even when turned off, all EOS bodies (other electronic cameras too) use a minute amount of power for memory and external displays.