My understanding is it takes three days, period.
My guess would be that it has to do with the life-cycle of the creatures.
Distilled water has been boiled and the steam was captured, hence distilled. It is more expensive than bottled water. Here in AZ we pay 40 cents a gallon, but in the grocery store it is about $1 a gallon. Plan on 3-4 gallons based on an average of a gallon of water a day.
There is nothing in it but H2O. It may not be necessary, but you don't want to feed them ANYTHING, not even the toothpaste to brush your teeth.
*S* //www.curezone.org/blogs/f.asp?f=59&t=15530.83