I have trained myself to sleep on planes and although I can't compete with JDiver sleeping on a trash can lid and mail sacks, I have slept on freight in Alaska when we were on float planes with several of the seats removed for gear.

But I am a short, small person.

My feet often don't touch the floor when seated in First Class so any seat that has a lot of adjustments is better for me. I tend to slide around on leather seats and have nearly been dumped on the floor when sleeping with my seat belt less than tightened down.

Someone my size has many advantages on modern aircraft not the least is smaller clothes to pack and more room for the person seating next to or beside me. I seldom recline my seat my than one click.

Would I pay extra for a lie-flat seat on a day flight. Not a chance.