I've flown Los Angeles to Australia; Los angeles to Rome many times, and agree with all the above. Keeping hydrated and walking about/flexing your legs as often as possible is very important. I always get an Aisle seat and also try to sleep as much as I can, it passes the time and helps with jetlag. (Booze makes jetlag ten times worse, but luckily you don't drink). But a long flight is a long flight I'm afraid.