I've flown JFK-LHR about 8 times in the last 10 months. My favorite "flight comfort/mileage cost maximization technique" is to upgrade the return if, and only if, you plan on sleeping on the way over to LHR and have secured a row 31 seat. When you eat before boarding and sleep right after takeoff. you don't miss out on much by being in 31. With a bag on the floor for a footrest, ambien in the system (after reaching cruising altitute - safety first), and some good headphones, I find it pretty easy to sleep in row 31. On the way home, tired from travelling and working, the upgrade during daylight hours makes the trip home more interesting and enjoyable. Much easier to work, eat and relax in the business class cabin.