To clarify my last post, my opinions are just that, opinions, not facts. No one really knows when a bearing should be replaced, unless it's tested (or catastrophically fails). That's why OEMs supply replacement specifications; they can't test your bearings and don't want you to be unhappy with their products should they fail.
Further, my opinions have been developed over many years of industry experience (I used to be an application/design/manufacturing engineer for Dana), including many conversations with bearing application/design/manufacturing engineers and site visits to the bearing manufacturing plants.
To be clear, the only way to positively determine whether a bearing (like a tapered roller bearing, the type used for automotive wheel bearings) should be replaced is to assess them the way the manufacturers do in their quality labs:
mount the cone on a test shaft,
mount the cup in a test housing,
assemble the two and
spin them under an axial design load
while measuring the runout on either the shaft, hub, or both.
This indirectly indicates the amount of clearance, under design load, between the load bearing surfaces. You then compare these data with the design load clearances. If the clearances (as indicated by the runout measurements) are at or below the design load clearances, the bearing is good. If the clearances exceed the design load clearances, the bearing should be replaced. As a practical matter, these clearances can be exceed by a fair amount and the bearing will still perform its intended function. namely protecting the major components it (they) supports.
You'll never see this in a youtube video, because, despite the fact that this is the de facto industry standard for testing, it is considered to be proprietary by all manufacturers. Furher, you cannot "test" a bearing in your hand and determine anything other than the fact that it is a bearing.
Obviously, this is impractical, to say the least, for even professional mechanics, not to mention impossible for home mechanics. That's why the OEMs publish recommended replacement intervals.