It may be advisable to hold on to your COVID certificates a while longer. Existing certificates can also still be used for travel if need be, as long as they comply with the destination country’s entry regulations and their QR code has technically not yet expired. The QR code for each COVID certificate is technically valid for two years from the date of issue.
Existing certificates in the COVID Certificate app are only stored locally. It will therefore still be possible to display these in a reduced form even after the certificate system has shut down. For more information on displaying certificates in the app, please see the FAQ "What's going to happen to the COVID Certificate app?". All other functions in the app are no longer available.