I have done very well on my DXB-BKK & BKK-DXB over the last 2 years but before I went 4 years without a single OP-UG, they will not upgrade unless the flight is full in the lower class, (I think they will also upgrade Y pax so they can accommodate stand-by's).

Another factor to consider is that they have increased capacity with the A380 on the 372/3 route so possibly fewer UG's for a while.

Who gets a a UG is a mystery to me, obviously Gold then Silver but there is more to it because there must be loads of Gold & Silver flying that sector but I seem to do very well.