PW local workspace copy - behaviour/when to purge?

Hi All,

we're running PW with integrated Microstation, OpenPlant Modeler etc.

I understood that, when opening documents from within PW explorer they are copied to local - along with their related workspace files.

In our workspace we had recently added a new DGNLIB and removed an old one. I experienced, that setting from the old DGNLIB was still "active".
While browsing through the local copy of the workspace I found out, that the old file is still stored locally, and the new file is in the same directory.

In case of workspace configuration variables that point to paths instead of files a.m. behaviour ends up in applications using old and new configuration settings together. 

My expectation was, that the local workspace in use is always looking like the PW stored workspace. In fact, the local workspace is a sum of workspaces.

Is something wrong with PW workspace download/local copies? Or do I have to ask all users to purge their local workspace, whenever I made change?
BTW: When should local workspace be purged in general?

Thanks for your answers in advance.

Thorsten.