Gs appearing for flights

When I booked my flight for MJB next month they only had UC on the way out and not inbound. We always get to the airport in time to get front row bubble seats, so no probs.
We had to call VA last night to change DDs flight from San Fran, as she has decided to extend her stay. So while I had them on the phone I asked about availability for the return leg, confirmed no Gs available but did say the cabin was not full.
Is there any pattern to Gs appearing or is it literally checking everyday, anytime of the day/night to see if they appear.
I know once I turn left, I wont ever want to turn "the other way" again
We had to call VA last night to change DDs flight from San Fran, as she has decided to extend her stay. So while I had them on the phone I asked about availability for the return leg, confirmed no Gs available but did say the cabin was not full.
Is there any pattern to Gs appearing or is it literally checking everyday, anytime of the day/night to see if they appear.
I know once I turn left, I wont ever want to turn "the other way" again
