I first did not use the reserve, thinking heck, I have a fuel gauge and I monitor the mileage on the trip counter. Then I took a tour in a hilly region of the state where the hills affected my consumption, the remoteness affected gas availability, and I realized that I do not understand why my gas gauge works the way it does (slow top half, quick bottom half of the tank). Now I use the reserve, and yesterday, for the first time this season, I turned it to reserve because I had been doing daytime interstate driving and was faster and more aggressive than my normal ride, and so used more gas.
It is great for the day that your ride does not conform to your normal ride profile.
Also, if you work the lever occasionally, it does not dry rot.
'95 Kawasaki Concours
Sold my Vulcan
I do LOTS
of dumb stuff. Riding is only one of them.