Nubians are seasonal breeders and their usual breeding season is fall, even though some does come in heat as soon as August and some will keep cycling well into early spring. Since we got our girls in spring, we had enough time to decide what to do about breeding. Goat lactation lasts about 10 months and goats need to have babies to have milk and you need a buck to have babies. So it's the same cycle every year, breed in fall for spring babies, milk the does from spring into late fall for 10 months with 2 months dry period.
Bucks are a whole different species than Nubian does. Once they come into rut, they perfume themselves for the ladies by urinating on their faces and legs, the urine dries up into a thick layer that has a very distinct odor to it. Some folks are bothered by the smell of a rutty buck but the ladies love this stuff. The bucks also exhibit other behavior that by human standards is considered disgusting. Herd sire is 50% of the herd so it pays to really chose carefully. While each doe will pass her genetics to her offsprings, the buck will pass his genes to the entire kid crop.