I did 38 500 km on my Scrambler FT since last may. This is my only bike so far, and I did long trips - over 700 km per day (excluding highways - I try to avoid them, because they're boring). I got 30L and 20L Kriega bags, which for me is enough to pack a lot of things for a long trip. I also travelled with a tent mounted on top of the bags - no problem at all. I can't compare riding to other bikes, because it is my first motorcycle ever. Technically - no problems at all. I do maintanance service regularly. The only thing is, it started to consume oil after 30k km, and it is the second Scrambler I know that has such an issue.
I'm 173 cm height and I got used to the seat. I do stop every 150-170 km for refuelling, so It's hard to say if you can ride on it all day long

I also stop a lot for taking photos. I got the bars lowered, and now for me the comfortable speed concerning windblast is below 150 kmph. The wind was the issue when I got standard FT handlebars, which were a bit too high for me. But I'm completely in love with the bike and even comparing to Triumph Thruxton I tested, I was glad I chose Scrambler.
The best mods:
- exhaust (I got IXIL RC2 - sound and power)
- rear sprocket from Panigale (longer gears for touring)
- lower Rizoma handlebars
- suspension change to Andreani front and Ohlins rear
- Brembo brake pump
But I did almost 20K km without those mods, and it was still a nice ride.