Yes, there is a site option to adjust the maximum milestones available, but it can only be adjusted by Luminate Support. Please Contact Support and provide the solution ID.

Once Support has increased the amount through your site options. Next follow these steps:

Steps to increase the limit:
  1. Click Fundraising > TeamRaisers
  2. Find the desired event in the list and click Edit
  3. Once you go in to edit the event, skip to step 3. Select Event Options
  4. Then on the left navigation bar, under related actions, click Edit Advanced Options
  5. It will be on part a. Define Fundraising Options
  6. Scroll down through the settings, and identify "Maximum Number of Milestones:"
  7. Increase the limit and click Save