It is stated that the Vault Pro thick client wil not release a license as it polls for ECO changes every 5 minutes. Apparently this is hardcoded http://crackingthevault.typepad.com/crackingthevault/2012/05/vault-licence-release-behaviour.html
This casues issues where license pools are being used to the max and not released.
I would like to see the ability to adjust the ECO polling so we can set it after the std license timeout if required.