It's what airlines and other industries use after psychological studies. Everyone has a different breaking point. They tell you the plane is delayed 45 minutes and then delay it another half hour and another because a few short fuses will come up the first time and complain and then a few more after 2nd delay and a handful after the 3rd one and so on. Once you complain once, its rare youll complain again - youll resign to your fate/know it wont do anything. Prevents mass stampede to counter if they told you its a 4 hour+ delay.

That's how it's only 2 weeks became a year with no resistance.