Some more interesting insights. I became curious about the % spend required on UA metal. Of the 200+ people who qualified for GS, about 130 of those also entered data for their yearly spend (PQD) on UA metal. So I calculated a ratio (percentage) of UA metal PQD / Total PQD for GS qualifiers. While I knew the ratio would be high, I never expected it to be so high. The GS group are so loyal, that their % of UA spend for total PQD is above 98%. This is astounding. I was expecting a ratio in the 70-80s.

Furthermore, it appears that GS requalifiers have even a higher ratio than new GS:

% Spend UA Metal PQD of total PQD (New GS): 94%
% Spend UA Metal PQD of total PQD (Requalified GS): 99%

I can see now why United loves this program. Once people get a bite of the GS bug, their spending increases, and they spend 95%+ their fares on UA metal. This makes complete sense from a marketing point of view. The lack of a spend threshold leaves people guessing at the end of the year. Because of this, people continue to spend their air travel dollars on UA.