Here are a couple of documents referring to ID's and Keys.
Note: ID - The ID of a node is a unique identifier for the node itself. If the node corresponding to an entity is destroyed, and a new node is subsequently created for it, the new node will have a different ID, but will have the same key.
What version of ADDM are you on?
It will almost always be a different key.
when you write key you refer to ADDMIntegrationID or ID?
I read the link send by Shine and I understand
Host1 -> ID1, Key1 (destroyed)
Host1 -> ID2, Key1
The key on the Host which is used to populate the ADDMIntegrationId quite frequently changes - e.g. is the OS is updated.