The fascinating part of this whole discussion is the wide variety of what is "best". The various opinions and especially strategies are interesting to say the least. None are wrong, all are correct... Because it all boils down to each individual and each situation.
I'm actually surprised by the amount of non monetary considerations. And even not directly related to the comfort level during the flight... I'm impressed by the deep thoughts put into overall strategies considering the entire trip. It makes a lot of sense. If I had thought through the impact of the entire travel experience rather than focusing on the cost of the tickets, I may have flown business more often and sooner in my trips over.
I used to just go cheap and felt i could tough out anything. My wife has shown me the path to a much better experience

Even though I could probably have afforded it without to much difficulty in the past, even my first trip to Africa, but i didn't feel good about spending the extra... Call it cheap or call it good business sense.. I was always focused more on the long term financial goal of being able to do what I wanted when I wanted in retirement, and to a large degree before. And honestly now it still makes me cringe to pay the difference... But my back, legs and feet hurt all the more and the cost is less important so we fly business on longer trips now. This discussion thread has definitely opened my eyes to considering the entire travel experience including lounges, etc.
I fully understand, respect, and agree with those who want to save the money and go economy. I do not follow the thoughts on having all year to pay for it, if you can't really afford it. But my mind doesn't work that way so I don't have to understand it, I can still respect the decisions.