Maybe once a year, if that. Once every couple months, I'll run up to 3/4 throttle. 5100-5300 approx, just to keep it cleaned out in there, but only for 20-30 seconds.
I'm with Curmudegon; I see no reason to work them hard; Mostly I'm between 3600-3900RPM's. My top cruise is 4400 at 36 MPH, but...