Our Confluence license expires at the end of June 2022. While we do not lose access to Confluence, we lose 'support', which means we are unable to update Confluence after that point. If anything breaks or is buggy, we're out of luck. This may mean open security holes or non-functional behaviour down the line, as other systems update and evolve. Additionally, Atlassian is discontinuing all Server products by 2024, regardless of license status.
Regardless of support status, our approach to Confluence has always been a bit hacky. The 10 user limit, for example, has led to sharing logins to allow everyone to edit the wiki. While a convenient workaround, this results in a significant potential security hole.