I grew up Missouri Synod 60 years ago.   We went 3 years once a week , Sat. mornings, 2 hours, for 8 months.    If your minister is a good teacher and uses the right resources you can get it all in one year.    The old minister had us sit in chairs and lectured for 2 hours.   BORING!   3rd year we had  seminary students.    They used different study materials and I actually learned something besides showing  I was a VERY good memorizer.   ECLA  Lutherans don't require 3 years.   Presbyterians  did it for our kids in one year of Sunday School time.    Quality rather than quantity.