Peak torque is around 3000 but adequate (90%) torque of 40lb.ft is reached around 2100 rpm. Remember in any gear peak torque = maximum acceleration. However you must change gears and the rpms will drop. Based on my gear ratio and staying within good torque range, my shift range is about 2200 rpm.
So if the gear ratio on your bike suggests 12 mph is somewhere around 2000 that's not a bad shift point for cruising. My 2nd and 3rd gears are really close ratio so I tend to go through them in a few seconds and end up in 4th in the city and 5th by the time I have gone halfway up a highway on ramp.
Racing light to light or on a track, you would be quicker shifting at 4500 WOT the whole way but that's a different story.