The Classic UI will be shutting down by the end of October, therefore after that time, you will not be able to make any changes to campaigns via the Classic UI. However, you will be able to activate or deactivate those Campaigns using the Standard UI (they will continue running).
At the moment, the Standard UI does not allow you to View or Edit the evergreen campaigns that were created with Classic, so it would be best to copy the campaigns manually from Classic to Standard by reviewing the definition in Classic before it shuts down. Thanks rkansal for this info!