The bearing is an interferance fit on the outer race to the wheel, the axle will slide in with hand pressure. When you torque the axle bolt you tighten the spacers to the sides of the inner races to prevent them from turning on the bolt. A little greese on the axle bolt is to prevent corrossion so you can get the bolt out again. If you change tires every year no big deal. If you only change tires every 5 years that axle bolt may get hard to drive out.
You are correct about the outer race and the spacers on the inner race, you also have seals on both sides, packing grease behind each seal acts as a moisture barrier, however you will always get condensation through extreme temperature changes. I can say the largest problem / root cause of bearing failure is improper installation , the second being taking short cuts and putting shielded bearings in where sealed bearing should go. Theoretically our Versys could use shielded bearings since we have wheel seals protecting them, that would be a mistake, sealed bearings are the correct application.
I am not a mechanic, however I have installed 1000's of bearings, some very expensive bearings, that were in short supply during the Vietnam war ( helicopter bearings made by SKF ). High spots on a shaft or high spots in a housing, will distort the bearing and cause premature bearing failure, this was shown to me by SKF engineers , hard to believe that a 0.005" high spot on a 2 inch thick spigot could distort the outer race housing by 0.005". So if you have premature wheel bearing failure, have a close look at the housing and shaft, look for shiny high spots, make sure you are careful installing the new bearing, if you don't have a proper driver, you can use the old bearing to drive the new one into the housing, make sure everything is going in staright. I used bearing heaters and dry ice on larger bearings ( wax pencils are made, colour coded for the safe installation when using heat).
95% of what I just posted probably has no application when applying to the Versys --I figure if I keep posting stuff like this, all those thoughts may just leak out and never come back