I use brine when I do turkey and such so I figured why not do it to the chickens too? Thats my reasoning I figured it wouldnt hurt any. I took them out and froze 3 and we will be eating 1 in a day or 2 so that one is in the fridge.
Many moons ago when I worked for a place that did broasted chicken, we would marinate in the salt solution overnight. I would think that would be enough time. I do that with my turkey and also pork roasts (they are so yummy that way........).
I guess I should clarify what I do- not really brine. I put mine in a 50 gallon barrel of ice water and a whole box of salt for 24 hours. Not nearly the concentration of a true brine, but the salt helps break down the tissue, and keeps the water colder.