ISettings and IPackageSourceProvider have events about changes to settings. However, the only place this appears to be used is in ExtensibleSourceRespositoryProvider and the only place it appears to be raised is in VSSettings when solutions are opened or closed.

The easier option would be to make ExtensibleSourceRespositoryProvider subscribe to the solution open and close events directly and remove all the configuration event code.

Alternatively, events should be unsubscribed properly, probably by making everything related IDisposable and making sure they get disposed correctly.