Hey Buddy - I usually leave it plugged in 24/7. BUT - my PC even supplies power to it when shut down, so I switch the PC off at the power swith so the 24c isn't powered-up 24/7.
SO - if after you shut your Mac down, all the lights go off on the 24c, then just leave it alone.
If the normally blue light turns red, then disconnect the 24c or switch off power to your Mac.
Hope this helps ;-)