I read on another thread that it is suspected that op-ups are "assigned" over 24-hours in advance. Is this true?

I'm hoping that I am now eligible for op-ups now that I am a part of Skywards. Doubt I would get anything on LHR flights due to all the plats, but there are tons of op-ups on the flight home to DUR, as Y is always very oversold and J empty (2-class plane). Very status-light flight too.

Also could help that I know most of the staff there, as it is always the same staff checking in at the J counter and working at the gate.