Trial licenses that are not managed by Power BI: Are they reusable for other users?

As far as I know there are two possible trial licenses in Power BI:

1. One is managed by Power BI itself and can be activated by users themselves by clicking on the "Try Pro"-Button.
2. The other is managed by AAD and can be assigned by a license admin.

My question concerns the licences described in bullet point 2. 

When trying to activate the test licenses, the dialogue states, that in whole 25 licences are going to be available:

Question:

Does a licence disappear after being used for one month? Or can it be assigned to another user who can use it for another month?

Background:

I consider using those licenses for training purposes. I don't want to spend my precious PRO-licenses for users that might not user Power BI afterwards (but of course never want to give back a license). Additionally, the Power BI managed Trial license option disappears when we set the licensing information link in the Admin portal.