For practical purposes I would propose that an endurance event is an event that takes anywhere between 8-36 hours to complete. I.e. it is an all day event that requires food and drink intake during the race, but is not interrupted by sleep or recovery. Multi-day events with mandatory rest periods, such as stage races are also included even if the individual stages are less than 8 hours in duration.
However, I do exclude self-supported events that run over multiple days. These are races where the participants are responsible for logistics and need to bring their own support crews. Furthermore, I want to exclude supported multi-day events, such as randonneur rides that don't have fixed rest periods.
The emphasis of this blog is on races or timed-events, where participants attempt to finish with a certain placing or within a certain time. Most races are identified as such, but some are not, often for unrelated reasons having to do with permits or liability insurance. I prefer to ignore these fine points and call the event a race once a substantial number of participants see it that way.
This blog is for those seeking to improve their performance as measured by time or standing, rather than just worrying about getting to the finish line.