Marketo offers upto 10 custom objects creation. And around 3 or 4 millions of records. But, our business stakeholder are worried about after 1 or 2 year if custom objects records exceeds 10 millions. What will be best way to clean up the custom objects data or Marketo offers support in this case.
If you are concerned about the limit, Marketo support can expand it for you. For cleaning up the data, I would suggest using the REST API to backup your data and delete Custom Object Records as needed.