Russia is a huge country and therefore in the Trans-Siberian marathon we ride 500-700 kilometers a day. Frankly saying, it is not an easy walk. However, not so difficult. We overcome this distance in about 8 hours stopping every 150 kilometers for a meal and rest. We also pretty often go off the road to take pictures.
Our average speed is 110-120 km/h and the roads are mostly straight and with a good road pavement.
And in the evening we usually leave our bikes near the hotel and go for a walk in the city. Moreover, we have parts of our marathon lying in amazingly beautiful places where we spend few rest days.
Don't worry about distance, it's a cool challenge!