If you delay to breed or craft the quest Dragon, it means that you lose valuable quest points for days.
At the same time, you also delay to reach the 2nd decoration, which gives 100 points every 4 hours!
Along with that, as Rfs04 correctly posted, 2 x 12 hours quests give less points in total than 5 x 3 hours quest during the day and 1 x 8 hour quest during the sleep time.
So, the sooner you breed/craft the Quest Dragon, raise him to 10 and put him in the right order of the quests, the better chances to complete the event, otherwise game is over!