Don't forget the online booking bonus now for Y (30%) which means you will hit that 25000 miles mark for your award on United
I am used to booking return ticks, outbound in F, return in Y; then using miles to upgrade the return leg.
On a BEY-DXB-SYD trip this earns me (including online/tier bonus) 36636 on the outbound. And 16036 on the return leg, which is enough for a one way upgrade to J.

Those points save me a good $1000US (instead of paying to ugprade to J).