Good to know re: IAD. Normally I am about 2 hours check-in. But Super Bowl Sunday 2023, there was some bad weather predicted in northern MD later in the day, so my ride didn't want to deal with it. Polaris, *Gold, to Europe somewhere. Agent nicely mentioned that I was a bit early. I explained the later in the day bad weather scenario. And without any of the 'we'll do you a favor one time' snark, she said, 'OK, no problem'. I was not aware of the 4 hour rule in the US (but acutely aware of the 3 hour counter opening at many non-US airports).