Re: How long before you dry up? Plugged ducts....
If you let your daughter continue to nurse just the one time before bed each day, it would probably help a lot with the plugged ducts.
I've noticed even with my younger toddler (only 19 months) I don't have so much milk just sitting in the breast in between nursings even though he still nurses a lot. Maybe if you continue to nurse just that one time a day your body might be better prepared to wean once your daughter is a little older.
ETA: And I think your breasts should function just fine as long as you don't end up with an infection that isn't properly treated.
K. Sophia - Mama to my little lactivore, the amazing Mr. X (11/10).