Batch Purge Files tool in the Purgers tool group of the Project Cleanup tool-set can help completely purge multiple external project files all at once, behaving exactly the same as opening each project manually into Revit, running Revit Purge a few times, saving the model, and repeating the whole process many times.
When the ribbon button is clicked, an alert box shows what will be done next.
If the Yes button is clicked, the tool will ask for what external project files to care about.
If the OK button is clicked, the tool will purge those project files one by one. An information box will finally show up to report what have been done.