Terminal Server now will expire licenses every 90 days and reissue them as needed. This way, if a client pc fails you can recover that license after 90 days when it expires. Before the license would just stay issued and there was no way to get it back. There was an update for this and it may have been included in SP2, not sure though. I loaded the individual fix after I installed the licenses.
If you see temporary Terminal Server licenses with expiration dates then you need to load a license pack.
Dev