by Ken Task.
If you are not willing to maintain security fixes/patches, etc. even on a site that has maintenance mode on or some other form of 'protection' (site login required, etc.), advise archiving (site backup) and remove. If there is a domain name, etc. that goes with it, place a 'placeholder' page at web root for that domain. In the event your customer cranks up training again, could restore the site and upgrade in a matter of minutes.
My 2 cents ... of course!
'spirit of sharing', Ken