I ride an Ultra, but I think we're talking about the same thing.
I watch the watts/amps. That tells you exactly how you're loading the motor to my way of thinking. If you look at the charts, my interpretation of them anyway, says rpms are not nearly important as some say (within reason). We're talking electric motor here, an absolute torque monster at that, not a small displacement 2 stroke motor that needs to stay in a narrow power band to make power.
To put this into practical terms, say riding on level pavement, I very often leave a stop sign in 4th or 5th gear, finding it very easy to keep wattage under 200w or even 150 as I accelerate in no particular hurry. That's VERY low loading that can't possibley hurt a thing.
Try that from a stop while half way up a hill, maybe while in a hurry, and you're going to see wattage well over 1000w. THAT'S a significant load that could have been minimized by dropping down to 1st or 2nd gear.