The perfect time to leave a party. When fun has been maximized and only the crying or problems remain.
The father looks at the wife and says “max fun” at the gathering. The wife then gets the kids together and they leave all having had a great time. The adults have a mutual understanding that the fun has been maximized and often leaving early they will miss the end of the party, but they also miss the problems. They move on the the next event and are all happy.