ok look: to answer your question because eveyone is going to tell you different, i'm a mechanic, and the simple answer is the more you spin your engine the more wear you are going to get. That bike was technically never meant to go over 55. thats why when you ride right around 55 mph with normal gearing it feels great. feels even better if you have lowered your rear sprocket teeth.
regardless, its totally fine to pass people or mess around with your buddies and pass them at 80-90 mph for short periods. but i'm telling you from experience that if you ride up here all the time you are going to have issues sooner and more frequent than people that dont.