I don't know if this is a simple question but I'm starting here and defer to the United experts re: whether it should be a stand-alone thread.

I have 180K United miles that expire March 2020 (my husband and kids each have less than 20,000 miles in their accounts because I used Chase points to boost my balance for a failed attempt to upgrade to Business on our last int'l trip). We have no status and only fly 2-3 times/year. We are planning a Feb. 2020 trip to Singapore, but I'd rather fly on Singapore Air and pay cash/Chase points for Premium Economy/Business than fly United on economy and use the miles to be waitlisted for Business again (no PE offered on the nonstop UA flight to Singapore). I know how hard it is for 4 passengers to get upgraded to J class with miles when we have no status. I thought I might try to use United miles to upgrade on SA, but I see on the Star Alliance page that you cannot use miles to upgrade on any SA A350, A380 and 777-300ER aircraft flights (which rules out our flight).

I vastly prefer nonstop flights given a missed connection debacle on our last int'l trip, but I see an option to fly confirmed J class to Beijing on UA metal and then PE on SA to Singapore (but with only 1 hour and 10 minutes for connecting time--isn't that insane to try to de-plane, go through customs, and board again in 70 minutes?). Would you do this to use up our UA miles? Let me add that I don't think we'll be doing another int'l trip after Feb. 2020 for many years due to my husband's rigid work schedule (he has to work when our kids are out of school at winter break, spring break, and summer, and our eldest starts high school in 2020 so we won't have the random Feb. and Sept. breaks that the kids' current school offers). We will still take 3 or 4 day trips and could try to use UA miles on domestic flights, but I know those saver awards are difficult to get and we would have rigid dates.

Finally, the last bit of background is that we have a trip to Tokyo planned this Sept. on SA and I created an SA KrisFlyer frequent flier account thinking we would accrue some KF points for our Feb. trip. I had thought I'd supplement with our Chase points and try to upgrade from a PE seat to J. But given how few miles we'll get from this flight and the low likelihood of upgrades on SA as well, should I try to switch the miles credit to our UA accounts?

Thank you for reading all this and helping with any advice!