One possibility: When we flew SFO-SIN nonstop last year, we took the aisle and window in a row maybe 3 rows from the back, and hoped nobody would choose that seat. Our strategy worked and we lucked out with one of maybe 5 empty seats on the whole plane between us! If someone had come, we would have offered them either the aisle or window. But on a 15 hour flight it was just wonderful to have the extra room.