First – I don’t know a real roadie who calls them century rides! They tend to talk about time and pace or the actual distance.
Second – It depends why you are riding. Training, touring, event. My club fitness rides tend to have a ride that stops for a tea about 2/3s or 10/15 miles from home so that no matter how far you’ve been the group has worked together and those who want to can have a stop or get back. The ride home can be as gentle or hard as without leaving people in the middle of nowhere.
Three – It depends on who you are riding with. The CTC group I also go out with stop at every gate to consider prostate issues and 11s and lunch and tea. But its the countryside and company you go for even on a long ride. My old racing club never stopped for anything except a mechanical on a proper training ride. You could tell if it was going to be proper by the number of drinking bottles they had with them.