We recently needed a workflow to bulk upgrade quite a few Revit files and I didn;t want to do that manually! Luckily, I have been working on some pretty cool application nodes for Rhythm and they worked great in this workflow.
First, let’s see this in action. Basically, we feed the node a directory’s contents (file paths), and it will chug along. The files in this example are from Revit 2016 and the graph is being run in 2017.

Next, what makes this possible?
This is actually made possible with two new nodes that I will be adding to Rhythm by the end of the week.
This allows us to open a revit file without it being visible to the end user. (Awesome!)
This allows us to close the documents we opened with a save option. (Great for upgrades)
Stay tuned for more workflows using these nodes! (UPDATE 05.16.2018 - These nodes are now called Application.OpenDocumentFile and Application.CloseDocument. You will have to replace the old versions of the nodes with these new versions. Any questions see the comments below.)
And here is the graph I used(Updated 01/27/2020)! (Download the latest version of Rhythm first) https://drive.google.com/open?id=1ecG56VG_reg1z-w3CBPlQb7lAzAQf1AD