Oddly, the Estimated Eyes switcheroo isn't as rare as one might imagine. The Dead did it 14 times, mostly in '90 and '91. Although the most famous occurrence is probably Colgate 11-4-77.
This 3 set beast looks awesome! I saw the final 6 New Year's Dead shows. The 3 set ritual slowly devolved. Proper 3rd sets in '86 and '87, then a 3 song encore in '88, then down to double encores in '89 and '90, and finally just Knockin' encore in '91. At that point, with Uncle Bobo having just passed away, the writing was on the wall. NYE Grateful Dead was no longer. Great that DSO carries the torch with such gusto.