Need help with a newb question:

When I have a reserve line, can I pick up open time over my reserve duty days several days in advance, or can I only proffer for OT during the 1000-1400 proffer window the day prior to a reserve day?

Trying to figure out if I can pick up stuff in open time in advance of the proffer window, so I can try to have some semblance of a set schedule and know if I will have a hotel room, since I am a commuter.