Keeping up with maintenance is the key to extending your ATV’s lifespan and that includes changing out bad wheel bearings when needed.
One way to test if a bearing has gone bad is to grab the top of the tire, and try to push it into and out from the Kodiak. If there is noticeable play or a clicking feeling when pushed, then the bearing is at the very least loose. Another method is to jack the wheel off the ground, pry the brake pads away from the rotor so you don’t feel it drag, and slowly rotate the tire to see if you can feel any roughness or "flatspots", those are the indicators of a bad bearing.
Sure, you can still ride the Kodiak with a bad bearing, but it’s not suggested and doing so can actually cause more damage. Once the bearing goes out, it could start a chain reaction with the ring gear, pinion gear, drive shaft, or worst case scenario, the tranny gears. If the state of the wheels bearings are bad enough, it could get hot enough to weld itself to the hub.
Best to nip this in the bud and periodically give them a once over. Youtuber Astro Camper has an in depth video walk-through on changing a Kodiak’s wheel bearings. It’s actually the Kodiak 450, but the process should be the same.