Definitely not a waste. Exhausted or not, I can't imagine that you would have done that successfully in coach. Aside from a typically noisier cabin, being 10-abreast in the back of the plane would have meant the person next to you was close enough that there would have been some shuffling, or bumping (shoulders/legs/hips), and the din of far more passengers chatting during meal services. If you are an aisle person like me, you would have had to get up for some passengers who wanted to stretch or use the lav. The person behind you could have been jabbing at the IFE half way through the flight, or a child could have been nearby crying from difficulty with the pressure changes.