This can be something of a game in economy long-hauls. In April I flew to Brussels -- shoulder season, mid-week, not particularly crowded according to the seat map. It was clear that some of the pax were regulars on that route, and they had figured out a routine for choosing assigned seats strategically so they could colonize center rows and stretch out overnight. I had hoped to do the same thing, but they had the moves and the timing. At least I had Ambien.