I would just enjoy the caviar and champagne on the ground and go into the flight with low expectations. I flew FCO-JFK F 2 weeks ago and the mystery champagne you’ve never heard of was fine. The purser was amazing. Very personable . I’m sure they will want to hear about your experiences over the years and enjoy it. They insisted on the turndown service ; the bedding is nice. Enjoy the 3 windows on the climb out of Heathrow and into DFW. It is what it is.