OP - excellent post, I don't know why I didn't see this before in UA forum.

I'm only at almost 300K, with 5 years of active flying. My current goal in next 10 years is to hit LT Gold if possible.
However, there is one question that keeps coming back to me. Regardless of how high of a status we have with a particular airline, we still have to fly that airline to see any benefit. (or at least their alliance partner)

I used to live in DEN, now SFO, so UAL naturally made sense to me for the past several years as primary airline. However, now there is a good chance I will be moving to SEA, and UA has almost no presence there.
I fly to Japan/Korea for most international travel so staying with UA still makes some remote sense given that their *A partners like NH and OZ have presence in SEA...but as far as domestic travel is concerned, SEA is nothing to UA.

Another recent example...my parents in law are visiting us in SFO and we are taking a short vacation trip together. I thought I would "show off" my lowly Platinum status via upgrading them using RPUs...except the flights were almost as twice as expensive vs. Delta.
So I am at this crossroad - do I pay almost double fare vs Delta to book UAL just so I can get them E+ or F for the remote chance if RPU clears?

Things like these make me question keeping my loyalty to one particular airline... I would have gone out of my way to ensure I'm flying UA until recently, but now I'm not so sure.