Usually single rank, top covered spaced about 4' apart. Allows for max air flow and exposure to sun for quicker seasoning.
Used to be a year, 18 months if I was lucky. This year I'll be at the 2 year mark, but next year and moving forward I'll be at the full 3 year point. I think I'll be alright, but if that doesn't bear out I'll look to space them after seeing what everyone is posting here.
I stack 3 or 6 rows tight together, no space. I’ve found that keeping wood off the ground, covered and protected from the rain is the key to dry wood after three years. Even in the shade.