As with almost everything YMMV. Of course my memory is fading, but back in 2014/2015 my wife and I had little joint items when we completed the AOS. In our case, she did have a SSN, so we were able to open a bank account, but we decided not to do a joint account, I did add her to my medical/dental/vision insurance since that was relatively easy, but that was about it (no joint utilities, car, etc.). We did take the Will route during her I751 stage, but that was a few years later. No one knows what a USCIS IO will focus on, but comingling a marriage in less than 90 days can be tough, and not everyone does it the same way depending on their station in life at the time. The main point here when someone is at the AOS stage, and considering the current political environment is to file the AOS ASAP with the required evidence. Comingling evidence can be gathered over time while the petition is being processed and taken to the interview.