World's 2017 tix

It looks like the tickets for next year's World's will be on sale soon! I've only been to one competition, so I wanted to check in and see those of you who have more experience have recommendations for choosing seats, etc. I remember reading somewhere that sometimes people don't show up, and you can buy cheap seats then move down the day of the competition to a seat that remains empty. I don't remember what competition that was about, though. Is that fairly typical for these large meets as well?

World's 2017 tix