The best practice is to create a new Miro board every 6-12 months based on your client's plan following this process:
Rename the Board to be Archived: Clearly label it to indicate the period during which it was used.
Create a New Board: Inside your Miro folder, create a new Miro board and name it Company Name_Designity. Password protect it if applicable.
Link Boards to One Another: On the old board, place a highly visible note linking to the new board. Repeat this on the new board, linking back to the previous one.
Update Portal Link: Change the Miro board link in your Portal on the client's details page to the new board's link: My Clients >> Client Details >> Update Info.
Inform Your Client: Notify the client about the transition to the new board.
Share with Your Creatives If Applicable: Please see "How To Share Your Miro Board" for instructions.