300 kilometres is a standard driving day on backroads, accounting for lunch and breaks. 500 kilometres is a sustainable maximum for highway driving. I only do the latter when I really have to. On long trips I estimate 200 kilometres a day, or 2 days on, 1 day off.

With a comfortable motorcycle this is perfectly reasonable. I have a 2017 V-Strom 650 and it's perfectly suitable for the task.

There are plenty of things that can be done to make it comfortable. For many bikes, if legs get stiff you can just stand up. There are some models that would be arduous, some that would be so comfortable as to put one to sleep, and some that are a good mix of comfort and performance. Either way, being in the landscape as opposed to in a car is a different and wonderful experience.

7 hours of driving a day for a long distance trip is hardly excessive, I know plenty of people who go 12 or even 14 hours when they wanna get somewhere quickly.