Back in May, the day after buying my new bike myself and Steve rode from Bamber Bridge to Southport.
This was 20 odd miles Each Way!
Southport route (roughly)
At that stage I had never ridden anything near that distance, ever. We were out for about 5 hours, 45 Miles.
This was a schoolboy error, dont ride that far on a new bike your not used to, the way back was a world of pain for me. Time needs to be taken getting used to your new bike, the riding position, how it handles.
Since then I have had no problems with the bike and am quite happy to ride long hours. Your body adapts if you take the time and take it easy at first. We have a developed a routine of getting off the bike reasonably often, to stretch out and let your bum go back to its normal shape!