Stock subscriptions have a credits rollover for unused assets of up to a year's credits. So, with a 10-assets-per-month subscription, you can accumulate up to 120 credits. And you can't go to lessen your credits, except if you license items.
However, if you have acquired credit packs, you need to use them in a year time frame, as they expire after a year.
ABAMBO | Hard- and Software Engineer | Photographer