Well, I just rode 10.000 km from Shanghai to Koh Panghan in Thailand and way back to China last year with my Yamaha YBR 125 G, and will ride again from Shanghai to Cape Town starting next April on the same bike (est. 28.000 km more).
I had absolutely no problems at all on my way, I know this machines have 2 main advantages: they are sturdy as hell (when rode at appropriate RPM) and easy to repair anywhere by anyone. Literally.
I know most people decide to ride extremely expensive KTM or BMW's for long rides. I have no doubt how much easy it is to ride on those, the comfort of 100 HP engines, big seats and all the electronics and stuff.
But seriously, when you are lost somewhere in the middle of mountainous regions in Laos or Yunnan, and your super fancy BMW electronic decides to break, you'll find yourself in a not pleasant situation waiting for expensive parts to be shipped where you are before you can continue on the road.
THAT will be the moment when I catch up on my small, 90km/h top speed, almost-bicycle-looking YBR.
That is, not to mention yet the 500+ km that I can ride with barely 11 litres of gas on the tank...
Oh, did I mention that my bike was just 10.000 RMB (~1250 euro) completely new from the official Yamaha shop in Shanghai?
But I give you one thing: Riding the perfectly flat and perfectly straight and perfectly long highways in Thailand at 90km/h it is just depressingly boring.
In the end it's always just a matter of choices, and usually budget.