I increasingly dislike back-to-back long haul flights enough to justify using inferior airlines and/or less comfortable seats in order to have one long and one short sector; nonstop obviously trumps connections of any variety, but they don't exist on many of my routes. In any event, what I really try to avoid more than anything else is stuff like arriving at LAX from a 10-hour flight and hopping on a 757 red eye to Boston.