We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Billy H" saying something like:
It's counter-productive; like so much else, the 'just enough' quantity can be gauged by experience or simply reading a manual or two.
Too much and it can blow seals out, leading to total loss of lube and severely contaminating the neighbouring components into the bargain. If those components happen to be safety-critical, like brakes, you can see the problem.
Another effect that might crop up would be the balls skidding on the races, rather than turning. If there's too much lube there's not enough friction there to keep rotation happening. Once a ball starts skidding, that bearing's pretty much looking at the end coming soon.
Pretty much; and leave space for the grease to go into.
As an illustration - most car makers use a miser's pinch of grease and generally the OE bearings last for ages. I think they use too little, but there you go.
The shortest-lived wheel bearings I've routinely dealt with are on m/bikes, where it's fairly common to replace them at around 50 or 60K due to the loading and harsh conditions. Even so, a good make of sealed bearings (Toyo) can double that.