Reorders of subscriptions automatically ship exactly one month after your previous order. If you order during the last days of the month (28th-31st) you may receive your order one or two days earlier than expected (e.g. If you order the first time on January 31st, your second supply will come on the 28th of February).
Reorders of single orders are less effective than taking a subscription, both in time-investment and price.
Subscribers also continuously benefit from discounts.