In case of indexing enabled, FLR session is closed right after restore. In case indexing is not enabled, there're actually two mount sessions in general case, where the mount server for repository is not the server initiating the restore (backup server or console). In this case, browsing session is not closed once restore is completed, but is closed once you log off the EM or after 15 minutes of inactivity (there're a couple of values
to control the behavior in this case). Mount session used for actual restore is closed upon restore completion.