You are billed monthly for the duration of the plan you select. If you purchase the 6 Month Plan your second shipment will ship the remaining product upfront. After the second shipment you will not receive anymore orders, and your card will be charged in 6 equal installments.
If you have purchased the 12 Month Plan you will receive orders in 4 shipments. The first two months will ship Stages 1 & 2 upfront. Months 3-6 will be payments only for the bulk order of Stage 2. Month 7 will ship 1 Stage 3 order, and month 8 will ship the remaining Stage 3 orders upfront. Months 9-12 will be payments only for the bulk order of Stage 3.