Based on the “Process Designer AutoSave” settings within the Status -> Settings -> Process Designer settings, the Definition can be auto-saved after the specified interval of time. Autosave only saves the definition if it detects any changes that have been made within the process designer.  

For example, in the below screen, the autosave configuration is set to “30 seconds” and after every 30 seconds, if there are changes within the designer, the designer will perform an autosave as shown below: