Replenishment subscriptions work like this:
First, click 
option on the Replenishment product page.
Choose your delivery frequency 
Then, check out.
Your subscription will start immediately after checkout.
Your first Replenishment will ship out the next business day.
You will be recharged at the duration you selected.
Multiple Replenishment subscriptions can be purchased at once!
Manage your subscription here My Account.
Recommended delivery frequency:
Every 6 months for one person
Every 5 months for two people
Every 4 months for three people
Every 3 months for four+