It's very slow to clean up a folder programmatically. Removing even few hundreds or thousands (plus responses) it takes a while. It would be much faster just delete this private folder and recreate it again.
Today the only way to clean up a folder is removal of a collection of documents from it. And folder never knows if this collection has all documents or only part. Would be nice to have a dedicated method on Folder (NotesView - ?) class to remove all docs from it.
RemoveAllFromFolder (NotesDocumentCollection - LotusScript)
Call notesDocumentCollection.RemoveAllFromFolder( folderName$ )