To be clear, this is not me/my wife's case; she's a friend from Thailand my wife and I have known for more than a decade, and she immigrated to the States in 2018 on a K-1. I just try to give her some guidance where needed.
I believe the ROC case was filed around September 2020, don't know what service center it went to. It had some complications to it, so I referred her to an immigration attorney. He just described it as "complicated" a few days ago when I was inquiring about the expiring 24 month letter. He also said it was the longest I-751 case he had ever represented. Had no contact with USCIS since filing, so it's a sweet surprise this morning. No RFE requests along the way either, so I guess the attorney knew what he was doing.