Sleep or not to sleep
If you can maintain 20-25km/h riding speed over 230km, that's 9-12 hours of riding time. If your stops are efficient, you can easily achieve that in daylight hours in summer. I still recommend you take lights to be seen by at dusk, and in case you're delayed by a mechanical. You're not likely to be riding for long enough to be sleepy at the half way (or better, 2/3) point. If the distance is much longer than you're used to, your speed will decline and your need for rest will increase. You may then have to stop if you don't want to ride in the dark. Aiming to stop for around 20 minutes every 3 hours, and extending one stop for a proper meal is a fairly typical approach, though many would stop less or more briefly. 

You use the word "tour". If that means more luggage than you're used to, then you should probably reduce your speed estimate a little, though your ride is essentially flat, to take account of extra drag.

200km in (max) 14 hours including stops is randoneuring (audax) pace, and the pace is very doable of the distance is. Example :My first 200km (230km including getting there and back) was well under that, despite being a winter ride (always slower).