As has been stated, using gasoline with more octane than your engine needs is a waste of money. A higher octane rating means the fuel is more resistant to detonation or pinging. In general, engines with higher compression are more prone to detonation. Other factors, like combustion chamber shape, ignition advance, and temperature are also contributing factors. Higher octane keeps the problem under control.

Once you choose a fuel with a high enough octane rating to prevent detonation, absolutely nothing is gained by using a higher octane rating. In fact, higher octane fuels actually have slightly less energy content, so using them unnecessarily could actually decrease performance and mileage by a tiny (probably not measureable) amount.

There's another factor at play. Modern vehicles have engine management computers that adjust for detonation, allowing lower than optimum grade fuels to be used without causing engine damage. Knock sensors tell the computers to adjust ignition timing. So it can be difficult to tell if your engine could use a higher octane fuel.

My personal experience with my 2 old Valkyries and 2 F6Bs has been interesting. My '98 Valkyrie Tourer runs great on any fuel, even the 85 octane junk they sell at high altitudes. In 175,00 miles I've never detected any pinging whatsoever. However, my '99 Interstate pings badly on hot days when accelerating hard with regular fuel. This could be because Honda used an ignition control module with more advance on the Interstates to compensate for the added weight. In the summer I always use mid grade or premium on that bike.

My F6B experiences have been more surprising. I had a 2013 that often needed premium fuel. I had been running 87 octane ('mid grade' at high altitudes) and on a hot day, I heard some brief pinging when accelerating. It quickly disappeared, then returned, then disappeared again, so the computer must have detected it and made timing adjustments to compensate. After that I began using 91 octane whenever the weather was warm. On the other hand, my current 2016 has no problem at all with 87 octane fuel.

I have no idea why the 2013 was so picky. Maybe I had an unusual bike that was slightly out of spec, or maybe Honda upped the power on those early F6Bs. That's happened before, as the '97 Valkyries performed better than subsequent years.