Do unused Draftbit credits roll over?

Each grant of credits is its own lot with its own expiry date, and the Credits page under Billing lists every active lot with the date it expires.

Monthly subscriptions grant their credits at the start of each billing period, including the credits from a monthly credit package. Those credits stay usable until 30 days after that period ends. In practice you always have the new month’s credits plus whatever was left from the previous month, and the leftover disappears a month later rather than on renewal day.

Yearly subscriptions grant twelve months of credits up front. They expire at the end of the yearly term with no grace window. One-time purchases expire one year after purchase, the 5,000 signup credits expire one year after signup, and credits earned through challenges on the Earn Credits page effectively never expire.

Spending always takes from the lot that expires soonest, so buying a top-up never causes older credits to go unused. Your balance only counts credits that have not expired. An upgrade that restarts your billing cycle has its own rules for credits, described in the plan change answer.