Edits reset on the 1st of each month (UTC). If you run out early, a credit pack keeps you going. Billed monthly through PayPal (card or PayPal balance); cancel anytime at paypal.com > Settings > Payments, and your plan runs to the end of the month you paid for.
Credits never expire. A typical edit uses about 150 to 450 credits (1 credit = $0.001), depending on how much music you ask for; big full-band requests can use 750. Clarifying questions are billed like a request; requests that change nothing are not charged. $10 (10,000 credits) is roughly 25 to 65 edits. Paying switches a free key to credits right away.
Questions? hi@aihud.net