nothing in particular. The only parameters I have are under 300 lbs "wet", and over 250 cc, so it's legal on the interstate, and a relatively quiet engine, and no electronics as long as I can get a functional bike that has none. I insist on being able to yank it into and out of the van in 5 seconds flat, with no ramp or other bs.
I have a shooting partner that is ex airborne, ex search & rescue tech that is now just coming up to his 69th birthday. He tells me that at his age long trips on a bike are becoming increasingly impossible.