While I am attending the training for XenDesktop today, we had covered the topic of License Server for Xendesktop.
I had raised the question to the trainer.

what if the license server go down, will all the existing connections or sessions been terminated automatically?

He had explained as the configuration in the license server and license files are design to prevent the point of failure in the scenario of license server unavailable due to any failures. You will be given 28 days period of time with unlimited seats in the event of license servers unavailable during the outage.

In normal scenario, assume your license server is functioning with 1000 seats, you will also allow to provision 10% extra within 28 days before you increase the purchased licenses. This will allow you to turn on extra capacity temporally in the short period.