Since all plans in Hunter are monthly limited subscriptions, unused credits don’t roll over. Your credits will reset at the end of your monthly billing period, and any unused credits will not carry over.
However, if you are upgrading or downgrading your plan, the credits left on your current paid plan will be automatically rolled over for 3 months on top of the new monthly usage.
In case of a Yearly plan upgrade, all the credits left in the current yearly billing plan will be added to an extra package on top of the new Yearly plan. The extra package will be valid until the expiration date of your first Yearly plan (the one you had before upgrading).
When you upgrade, the new subscription is applied immediately and a new monthly (or yearly) billing cycle starts over.