A lie-flat on 6 overnight flights a year (if only burning miles) would be burning something north of 300,000 K a year. Your spending patterns get you pretty close to that. The thing is declaring fealty to UA means you end with UA's products- there are honestly better C/F cabins out there you can redeem with miles.

I would be strongly inclined to see if AA works for your travel patterns if I was you, especially going to shoot for top tier. Some things to note:

- AMEX transfers to BA (very often with bonuses), BA Y+ ->C costs less miles (and you're in Y+ if the upgrade fails), and there's no copay.

- AA EXP, if you can hit it, is a better status than UA 1K on the free upgrade front: 8 instruments, not restricted by fare class. The downside is AA's coverage in Asia is weak (and a lot of their fleet is slanty seat C, not full-flat), and you're flying QF going to AU/NZ (or burning miles). The upside is CX premium class award availability to SE Asia is very good (much easier to get than SQ and every bit as good), and it's a really nice ride. (You also get JL and MH too.)