It really depends on what type of hens you have. There are early molting hens and late molting hens and between the two different types you could experience a molt time between 2 to 6 months. Most hens do not lay eggs during their molt but some types will. I found a great article that I think will answer your questions in more detail. Scroll to the section about Molt, and Estimating the Duration of the Molt! www.msstate.edu