John Scalzi has written on things he splurges on for travel. The main point is, "If there's an ocean involved, when possible, buy a lie-down seat."
I've never had one of those, and I wonder how much it would help for me. Unlike Scalzi, I can sometimes sleep sitting up, and in fact I prop myself up as much as possible whenever going to bed, but I can't always sleep lying down either.
On the other hand, I've never flown transpacific either, and I doubt I ever will, because that's too long to spend in a plane whatever the position. Ten-hour transatlantic flights I've managed, but lately I'm finding even a 5-hour transcontinental flight is too wearying. (I lost my bag in the airport due to exhaustion after one of those last year.) My last such trip I scheduled a long layover, and that helped. It would only work when I'm traveling alone, though, because B. has trouble with the schlepping around dependent on any airport transfer.
(Would I, as Scalzi contemplates, leave the airport during a sufficiently long scheduled layover? I did that once, but I think it was pre-9/11. No, I'm not navigating both security and transit. Find something decent to eat in the airport - easier now than that used to be - and spend the rest of the time reading. Much more relaxing.)
My number one travel rule - and this applies to any mode of transportation, car or bus or even foot as well as plane - is: Always spend more time at your destination than you do in total transit. Scalzi says he's on "a week-long trip to Australia" and doesn't say if that includes travel time. It takes the better part of two days to get there, and if that's part of his week that would leave him only 3+ days there. I find it too wearying even to drive an hour if I'm not going to be there at least 2 hours, preferably more, and one reason I don't take the train to the City is that it means a 2-3 hour trip each way. I'm not going to be up there for 6 hours, and even as a passenger that's too much.