I have the Mustang solo with a backrest. I can ride 25 hours straight with only short breaks where I get off the bike and it is still comfortable. The limiting factor for me is staying awake.

 

I have the wide vintage solo with the backrest. The standard mount for the backrest was too far forward for me, always felt like I was getting pushed forward. Then I found out that Mustang also made an off set backrest mount. With this setup I can ride from sunrise to sundown any day - every day!