Hi Clint,
the inventory policies will also be triggered by the Agent when it is offline. The results will then be queued to send them out when the Agent is able to reach it's SMP Server again.
The Inventory Data which has been send before, will stay in database until something new is delivered by the Agent (ok - you could go ahead and delete the computer ;-) ). Even if you change the Clients status from active to anything else, you will have to have the Inventory Clean Up Task running for that Asset status to wipe out the data (and free the Inventory license).