Since all plans in Hunter are monthly limited subscriptions, unused requests don’t roll over. Your requests will reset at the end of your monthly billing period, and unused requests will not carry over.
However, if you are upgrading or downgrading your plan, the requests left on your current premium 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 requests left in the current yearly billing plan will be added in an extra pack on top of the new Yearly plan. The extra pack 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.