Currently, if you disconnect and then reconnect again with a different set of exported local drives, you have to manually run tl-mount-localdrives. This could be eliminated by having some kind of "supervisor" daemon runnning in the background, checking the availability of the NFS SSH tunnel. If the connection is lost, and then back again, tl-mount-localdrives should be ran again. It would even be possible to display some kind of GUI dialog for the user, and inform him if he had some files open on the drive which doesn't exist any longer.
See also bug 2466.