Hi - I don't think we're on different firmware versions - 2.1.5 here too.
Are you looking at the conf file? I have the AutoOffMinutes setting and the AutoFrontLightOffMinutes setting in mine.
If (on your normal settings screen) you have a setting to automatically turn off the light which is separate to the sleep timeout, then you must have a setting to match somewhere in a conf file, otherwise how would your Glo know when to turn the lights out?
You haven't tinkered it out of existence have you?