Terminal Server License switching.

Someone contacted me about a message they were receiving when they log into terminal services about a license expiring.

Checking the TS License manager shows that whoever set them up set them up with temporary licenses and per device licensing.

I want to switch them to per user licensing but dont want to kill what they have.

Is switching to per user licensing going to issue temporary licenses again against the user rather than the machine or is it going to kill everything until the necessary CAL's are purchased/found?

Thanks in advance folks