I'm in 5th unless pulling up a hill or in one helluva head-wind.

 

55mph is 4th gear for me. I don't mind noodling along at 2,400 rpm but my bike definitely has a sweet spot @ 2,800. It also likes 3,500...and positively loves to wind out to 5K. Repeatedly! I never use 6th unless I can cruise comfortably above 80mph. But that's just me.