No, the minimum subscription renewal time is 2 weeks. On our product description page prior to purchase, it states this that there are no exceptions to this policy even for events that happen outside of your control. We recommend that you purchase more time than you think to account for any events that could delay your test. If you choose to purchase the 1 month subscription and an event occurs that postpones your Step 3 exam, you will need to purchase another subscription once your current subscription expires.
The reason we do not offer discounts for renewals or offer time less than a month is that this policy is commonly abused. Offering discounts to renewals creates incentives for students to renew and hand off subscriptions to other students. We'd rather not have to police this, so we do not offer any discounts for renewals.