I always take a short break on long rides, but usually not more then 5 - 10 minutes, stretch the legs, top off the water bottles, and grab a bite to eat. Most organized centuries have two or three break areas.

I have done a few 100+ mile days, but wouldn’t consider them a real century. 60 miles in the morning and 40 miles in the afternoon, a shower, nap and lunch between the two rides.