it doesn't say how long you have to be idle before it kicks you. i sometimes go idle for an hour or two while i go get dinner (sometimes leaving my character at a table with food on it) and i don't want to have to log back in when i get back
of course when it goes live people on PC will just set up a macro to move their character every few minutes.
ps3 users will be SoL...you would need a machine to physically move the sticks, or get their PC to spoof the ps3 controller over bluetooth and send signals for a joystick move...but that's far more complicated.