Have you done a 5 hour century? For me, the less stopping the better. Stopping means restarting, and restarting means getting warmed up all over again. Plus all the time slowing down, speeding up, etc...
I'm not sure what you are trying to say here...
I tried, but I can't find too many flat areas around me that I can do a full century in 5hrs. I'll have to hit hills and stops all over the place, so No I havent but I sure did try and it was no joke. Stopping all the time and resting = ez.
Slowing down once and speeding up once is no big deal when you get a 20minute break in between. You are quite rested.