I have done over 4000 motorway miles (1 hr each way) on my Tenere and it certainly comfortable cruising at 85 (highest I was prepared to do for a sustained period).

Fuel economy at that speeds drops quite a bit though. I get 50mpg doign 85 and doign 70-75 I can just about get 60mpg out of it so thats a 20% saving. Both are comfortable so it depends on if tiem is more important to you than fuel cost.