I have been looking at F award SYD-BKK vv and 2 weeks ago, there was nothing in December. Expertflyer showed a lot of empty F cabins. I found a few up to around Nov 28/29 but now they have some until around Dec 6. I guess they slowly release these. Award for Dec was open before for a very short time and a friend got the seat early this year. I think this could be the case for Jan - April as well. Jan was usually difficult to get but Feb, Mar and even Apr were quite easy from my experience past few years. I think they might change the way they release F seat. I normally fly F to BKK 3-4 times a year and started seeing a new pattern since last year. ie Nov 17, Looking for seat for Late April 18 but nothing around that time at all thru May/June. I don't think it's UA members that took all the seat. Then mid January I got a notification from Expertflyer and TG released a ton of F seat for Apr-June. They used to release everything then again at T-5.