Same for the priesthood, it's 6 years minimum. Alot of it now is to give the person and the order time to really be sure it is the right decision. They don't want to rush anyone or ket anyone make rash decisions.

Depending on the order the nun is they can be in a teaching order, a missionary order etc, so there is training. Enclosed orders might be different but nuns that are out in the community, doing hospice care, working with those in need, certainly require training