There is a comedian who tells a story about traveling to New Zealand for vacation. He recounts the misery that he experienced on his 17-hour flight and suggests that only someone who is insane would ever undertake the activity. Trans-oceanic flights are brutal, but can be survived with proper preparation.
Make sure that you have plenty of ways to amuse yourself. Bring an extra laptop battery and airplane adaptor for your computer, Smartphone or tablet. Most new planes have real power outlets available, but older jets will still need an adaptor to allow you to plug in. A pocket-sized surge protector is a great idea as well. Many older planes have very irregular power flow levels during flight. Most airlines offer in-flight Wi-Fi, for this type of trip it is worth the extra expense. Preload a few favorite movies on your mobile devices. If you do not, then you run the risk of having to watch something retched from 15 years ago; this will only make the airsickness worse. Be prepared to have a meaningless conversation for at least 2-3 hours with someone that you have never met sitting in the seat beside you. Be nice about this, remember they are just as trapped as you are and are looking to fill the boredom as well.
These tips can help save your sanity while traveling on a trans-oceanic flight. Granted nothing can make the flight shorter, but anything that offers an alternative to watching "Teenage Mutant Ninja Turtles: The Movie" back-to-back three times in a row is a major advantage.