After having problem to manage a large list of short-term users, I wrote a little Windows program to delete users by viewing the last time seen, and deleting 'old' users and/or sessions.
The program is attached, if anyone might need it. Pop a comment here if you find it usefull.
Although users are deleted, it does not seem to compact the database as system/store/disks space stay more or less the same. Maybe MT can give some comment on how to compact a UM database?
Anyways, enjoy.
Ekkas