The university of Georgia did a study years ago and they determined through extensive testing that it is best left for 10 days at 40 degrees. If its warmer, leave it hang shorter, colder and it needs to be hung longer. Of course as it approaches freezing the process almost stops or slows considerably.

If you do process sooner you should let it thaw and sit in the fridge for several days to let the microbes break down the muscle tissue for tender eating.