Delete old items if it exceed List View Threshold

I'm having a workflow that creates alot of documents in a single library. I know I'm going to exceed the limit of 5000 pretty fast. Old documents can be deleted so the question is: Is there a simple way to delete old files automatically?

The best way would be if there where a option that sharepoint deletes the oldest items in the list if it exceed the list view threshold.

The only way I can think of is to run a timer job / scheduled task that runs every night and delete the oldest files if it exceed like 4000.