I often end up with several devices listed in the trusted devices list, without any clue of what are the currently active ones, or even their OS and browser. That forces me to purge all devices and re-enroll them every few months. But let's be frank, that's barely a management.
First we need more information about the devices. Things that LastPass is probably already logging anyway, but chooses not to show the user. By adding the following fields we can start to have something useful:
Timestamp of last access / last time used
Timestamp of registration
IP + Geo IP of registration
Along these lines, it would be great to have some "obsolete device notification" that would ask the users if they would like to remove that device, or even an automated way of removing devices after (3, 6, 12) months of inactivity.