Well maybe you will replace them when they are 86 years old. Wheel bearings really aren't all that difficult to replace and piece of mind is worth the price of admission as long as you use high quality replacement parts. Historically, wheel bearings and drive chains are some of the most neglected parts of a motorcycle. Without a complete disassembly of the bearings, including cleaning them and repacking you just don't know if they are in top notch condition. On my every day bikes I replace the bearings every other tire change just to be safe. However I have been accused of being anal when it comes to things meant to keep me off the pavement. Each to their own.
You risk damage to the hubs by driving out the bearings that often. If the bearings are running smooth there is no reason to mess with them. Especially if using the high quality Japanese bearings like when the bike was new.
You risk damaging something every time you turn a nut or bolt on your bike. My point was we aren't talking about a two or three year old bike here. We are talking about a bike that is over 40 years old and sat idle for a good long part of that. If someone wants to disregard 40+ years of sitting idle, which is many times worse than being ridden and is hesitant replacing something as simple as wheel bearings than that is their choice, but wheel bearings on a motorcycle are almost as important as good tires and brakes. There are no idiot lights or warning bells that activate when wheel bearings go bad, so a tear down inspection is the only way to verify that they are still good. There is a remote chance that you might hear a wheel bearing going bad, but then again you may not. You may even "feel" a wheel bearing going bad, but by that time the damage is already taking place. I have yet to find a better way of checking wheel bearings than to take them out and turn them by hand while trying to put a little pre-load on them to ascertain any roughness, but even this is risky at best. However, if I am going to go thru all the work involved in taking the wheel bearings out of my bike, or any bike to check them I most certainly will replace the bearings at that point, especially on a motorcycle that is 4 decades old. The only way I might negate replacing old wheel bearings is if I couldn't locate new ones, but all bets are off on longevity of the old ones being reinstalled. My decision to replace wheel bearings every other tire change means they have anywhere between 12,000 and 18,000 miles on them at that point. I ride in rain and shine and I really don't want to have to worry about the condition of something like wheel bearings when I am on a long or short trip, so they get replaced every second tire change. Rarely is replacing wheel bearings a big deal when you already have the wheel off. Of course having a driver to replace the bearings is helpful, but in many instances not really a mandate. My decision to replace wheel bearings has come from over 50 years of riding experience, several years of which I spent on a law enforcement motorcycle. In my mind it made sense not to put complete faith in old wheel bearings that can have a huge impact on my health and safety. Your opinion may vary....I wonder if the Japanese engineers ever anticipated their wheel bearings would never be replaced after 40 years?