Before my current job my all time longest leg was 7:58 and that was an anomaly. Usually 2-5 hours. I never thought I would want to fly long haul and avoided it at my passenger carrier. Almost 10 years into long haul now and I don't find it that bad. Sleep when your tired. Eat when your hungry. Exercise when able. We normally don't stay in a time zone long enough to acclimate so I do OK. No one knows how it will be until they actually do it. Want to find out how our life is? Buy a few hotel rooms and go out and jumpseat a few trips.