No. Unused plan credits don't carry over to the next month. When your plan resets, you start again with your plan's allowance, and anything left from before is gone.
When your credits reset
Monthly plans: at each billing date.
Free, yearly and Enterprise plans: every 30 days.
A yearly plan gets a monthly allowance, not one pool for the whole year.
Credit packs do carry over
Credit packs are extra credits you buy on top of your plan. They last 12 months from purchase, and they carry over from one month to the next. Tomba uses them only after your plan credits run out, oldest pack first.
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