Well, Baylorgirl... when I was a BerkeleyBoy I always traveled coach too.
However, it was painful even when I was young, and I think that's true for anyone who is over about 5'9" or over 180lbs.
I travel international several times a year, and the total transit time is from 24 to 36 hours, with in-the-air time as much as 22 hours. It's very hard to sleep in coach and on some airlines hard to use ones laptop, as there is no power outlet. (American is much better for power, but only in some rows)
In addition, I always feel a bit claustrophobic and very tense in long-haul coach seats. Being able to stretch out and sleep is extremely nice!!

Keep in mind though, that I'm one of those very frugal passengers who have never bought a Business Class (let alone First Class) international ticket. I always play the upgrade game. On this forum there are many people who do pay for higher class seats, and they pay a lot!!! I can't imagine paying those fares myself, but many companies will pay.