I usually bank on around 12 hours overall for a 200
Yeah, that's about where I am. Compared to some, that's on the slow side of things, but on a 200km/300km it bothers me very little indeed. I'm happy to get round and still see people at the final control. The problem arises when you get into the
absurdly longer distances, which for me, are 400km+.
On average, the longer you ride the slower you tend to get, so if this is your base speed for a 200km is 12hrs then by the time you get to a 600km then sleep deprivation becomes an issue. I've only ever done one 600, and had no time to sleep and got in bang on the bell, exactly 40hrs. The same thing happened on PBP, 1200km in exactly 90hrs, with 3 hrs sleep. Never again. I'm not sure I've really felt the same since
The only reason I'd like to get a bit quicker is not for the satisfaction of riding a 200km quicker, but to accrue some time for Z's on anything significantly longer.