I am a 2MM lifetime Plat, and a 1K. I barely made it for 2017 with maybe $100 over the $12k required. I travel in economy for both business and pleasure, and my PQDs are about 50-50 split between the two. This year I am starting not to care already (I realize we're only in January). Like many of you said already, the GPUs are basically useless (I used them on domestic flights), they put 1K in boarding group 1 with everyone else (here in SFO sometimes the group 1 lines are super long), and no one seems to care that you're 1K anymore.
The reality is, UA is focusing on business travelers who travel in J/C or F. The rest of us who have shown loyalty really no longer matter.
So I'll get Group 1 boarding for now with Lifetime Plat.
Lastly, I am about 850K to 3MM. I've thought about making it there and then stop. But as they continue to take away benefits, I am not as sure whether I'd even want that. Or just do lots of MRs in the next year or two or four to get myself there without PQDs and call it quits.