No. Your WebCatalog data is not deleted when your subscription expires.
Some paid features may become unavailable, but your apps, profiles, spaces, bookmarks, settings, and other data associated with your WebCatalog account are kept.
If you subscribe again later, you can continue using your existing setup without having to start over.
Website login sessions, cookies, and other browsing data stored locally on your device are also unaffected by your WebCatalog subscription status.