Quests end usually because the allocated time for it runs out, or the prizes are all given out.
The host room (quest) was scheduled to be from 08:30 to 11:30, I think the extra time allowed was for those that may have just started it at around 11:25 and gave some time to play the mini-games.
Granted, not everyone can go through the games and tasks at the same speed. When I started, I saw that some people completed it in 20 mins, I took considerably longer about 45 to do it all. So any extra time I get is needed.