After retiring computer resources, corresponding licenses for Software Management Solution are not immediately reclaimed according to the Product Licensing web part (Home > Notification Server Management > Portal). Note that this issue could also be observed with other solutions that have agent-based licenses.
Software Management Solution licenses are not released by retired computers until the LicenseSynchronizeIntervalMins limit is reached, which by default is 4 hours. LicenseSynchronizeIntervalMins (a key located in CoreSettings.config) is the interval at which the resources consuming licenses are refreshed.
Once a computer resource has been retired, the interval set through LicenseSynchronizeIntervalMins must first elapse and then the "NS.Internal License Refresh Item" scheduled task must run before the Product Licensing web part will reflect that the license for Software Management Solution has been reclaimed.
7.1 SP2 MP1.1 v6 with point fix 3417720.
Targeted for 7.1 SP2 MP1.1 v11
7.5 without SP1 and all versions of 7.1 and 7.0 not listed above do not release the Software Management Solution licenses unless the old computers are deleted.