For NightCafe PRO subscriptions, you will be charged (and receive your credits) on the same day each month when possible (some months have fewer days than others). You can see when your next payment is scheduled under Manage subscription.
For quarterly subscriptions, credits for all 3 months are delivered in advance upon the first payment, and every next quarter (upon payment for all 3 months), unless you change your payment schedule by using pause, cancel or renew your subscription (Charge now) option.