I would say you're fully qualified for the Endurance Athlete label! Not that I know exactly, or have even seen a definition (just Googled it . . . no help), but that much riding should qualify you, no problem!

I have seen a definition for "Ultra Marathon" cyclists (from the UMCA) of riding 200 miles or more in one day (24 Hours). But . . . if you ride double centuries, you qualify for that too!

Best Regards,
Rick / OCRR