Licenses have expiration dates. The app can be updated as long as the evaluation license is valid. The app stops working when the license period ends. That means:
The smart system panels (issue-links, sub-tasks, issues in epic panel) are reset to the Jira out-of-the-box configuration.
No issue panels or wiki panels will be displayed in the issue overview page.
The configuration UI at project setting level will be removed.
The configuration UI at admin level will be removed.
Stored data in database tables are preserved.