My overall advice would be to try to put the application to the back of your mind and try to keep busy. These are your final days in the US! Live it up. Plan lots of activities with family and friends. Eat your favourite foods. Do all the things you'll miss after you move! I've been back exactly three weeks since my annual trip and I'm already itching for sunshine, warmth, friends, sitting outside on the porch having a drink and munchies, and easy relaxed days out! Yesterday my husband announced that it's less than 11 months until we leave again. 
While there is no genuine set start and end time, I'd say if you haven't heard by 4 or 5pm UK time, it's not happening that day.
All very logical. It's a tough order though because, and I think I speak for most of us, this is the very last piece of a very long puzzle. In my case, we have sold our house, packed our belongings that we plan to ship, made our shipping arrangements, well, you know the drill. I've had butterfly stomach ever since we sent in the application and documents. I was actually surprised at how relaxed I was over the weekend, but I realized when I woke up at 5 a.m. this morning, that it was simply because I knew I wouldn't get any news. I found I did relax at noon, 5 p.m. Sheffield time. I am spending loads of time with my family, and we are eating a lot of Florida seafood, which I shall miss. My husband is just as bad, I found out today he has been checking the return tracking number. We're doing the best we can, but it is an anxious time.
