If you check the search function - there was a thread about travel kits - what to take on the plane.
I've found these help me on long flights
1) Bottled water - you are not at the whim of the FA's... keep drinking it to. Airplane air is dry and for 8 hrs it's worse.
2) lip balm / lotion for skin -
3) A couple of good books -- of different types - don't take 2 mysteries since you may get bored of one for whatever reason.
4) Laptops are good - I like to write on the plan - games - movies - all good.
5) Get son to write a report - it keeps his mind off the length of the flight
6) If you can - when you book allow an extra seat between you so you can stretch out.
7) small bottle of mouthwash - toothbrush - after all that time - it will help perk you up.
8) Don't forget adapter for power plug.
9) tell son for every time he complains you will take $5 off his spending money on the trip. (I've got three kids- this works)
Live it up.
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TANSTAAFL - but if you work it right, FF miles comes pretty close.