Gary,
I agree, running with a single vault seems to disagree with the technical brief, but that is what PTC tech support told me to do.
There are multiple issues at play here, so this will be a really long post.
Vault Configuration
When I was testing this I had two vaults setup, a cache vault and a replica vault. The cache vault was set as the default target for site (remote site) and was connected to a single folder. The replica vault was setup with multiple folders and configured to allow automatic folder creation based on file count.
Synchronization Behavior
I was taught during PTC training that data created at a remote site (in the cache vault) would automatically be converted to replica data (moved to the replica vault) after synchronization with the master. PTC technical support initially confirmed that this understanding was correct. The technical brief also seemed to agree with this. From page 20:
If the original, cached content is moved to another site as a result of the synchronization process, the cached content is then converted to further replicated content.
Unfortunately, in my tests this movement from cache vault to replica vault was never taking place. After extensive testing by PTC they determined that it is working correctly, but both their and my understand was incorrect. The original content in the cache vault is converted to replica content after synchronization, but it remains in the cache vault. It does not get moved to the replica vault. This of course is a problem because my cache vault wasn't configured for automatic folder creation. Anything that was created at the remote site would have it's replica content stuck in the cache vault (forever). Since it only had a single folder associated with it, there was nothing to prevent unrestrained growth on this one folder.
Ad-Hoc Replication
In the process of testing I also noticed that any cad models, 3D thumbnails, or visualizations I accessed directly from Creo or from any web browser would automatically get downloaded to the cache vault before being sent to my computer. This is good in the sense that the next time someone else at this same remote site wants to access these files, they are already there. This is bad though because these also are going into the cache vault (which isn't setup for automatic folder creation). Changing the "default target for site" check box from the cache vault to the replica vault changed this behavior. Now all the ad-hoc, on-the-fly stuff is going to the replica vault instead of the cache vault.
Conclusion
Based on how data is converted to replica content after synchronization, I really only see two options. Either use one vault for everything (like I'm currently doing now) or make sure that the cache vault and the replica vault are both configured for automatic folder creation. I guess I don't see a good reason to keep the locally created, but now considered replica data separate from the replicated data coming from the master. Neither did the PTC technical support person. If you think about it, this is exactly how the master site is setup as well. We have the "wt.fv.forceContentToVault" turned on with a single master vault (with automatic folder creation). The cache vault at the master site is never used. All new content goes directly to the master vault. Why shouldn't the remote site simply work the same way?
If you have anything I can take back to tech support to show why this is a bad idea, please let me know. Thanks!
Tom