Downgrading Account: Do You Keep Leftover Credits?

Yes, you'll keep your leftover credits when you downgrade, but there are some important details to note: 1. Your current credits will remain on your account until the end of your billing cycle. 2. When your billing cycle refreshes, you'll be downgraded to the new plan. 3. At that point, your credit balance will be capped at 2x the monthly credit limit of your new plan. For example, if you downgrade to a plan with a 1,000 credit monthly limit, your balance will be capped at 2,000 credits on the next billing date. If you need more information about this process, please let me know.

Source: Credit Rollover After Cancelling or Downgrading Subscription