Once you have reached your capacity limit for registered domains, you can still create shared deals in a Best Partner Wins or Partner Collaboration scenario.
While you can create as many shared deals as you like, all deals should be qualified and only submitted after you've established a relationship and have identified a potential need for HubSpot software with the prospect. HubSpot will be actively monitoring for abuse.
Note: HubSpot sales reps have the discretion to remove any partner from a shared deal.