You can always upgrade your Premium boards one-off to Milestone boards, which will accept unlimited posts. You'll also receive the added feature of being able to play your Kudoboard as a slideshow.
The cost to upgrade to a Milestone board will be $11.00 USD rather than the standard price of $19.99 USD (as you will not be responsible for the $8.99 USD amount that is the purchase price of a single Premium board since your board has already been upgraded to Premium using a credit from your package).
To upgrade your Premium board to a Milestone board, you can follow these steps:
1. While logged into your account, view your Given Dashboard.
2. Next to the board you'd like to upgrade, click the upgrade button (next to Posts).
Alternatively, you can follow the steps outlined in this support article while logged in and viewing the board.