When you have a teenage son. I told my son to take a short shower. To me a short shower is about 10 or 15 minutes. 45 minutes later he wandered out of the shower with the water coming out of the tap luke warm.
Crap. I've got five other kids that need to get in there and have showers or baths. And my son sucks every last ounce of hot water out of the system. Great.
Next time, he may get the water cut off at the five minute mark.