When I sold high speed centrifuges in the drilling industry we would monitor bearing temperatures   You could watch the temps rise in a bearing with a lot extra grease pumped in.  These were spinning at 2,000-2200rpm. As for Dexter hubs maybe the bearing type and fact the outside end of the hub is open for grease to exit around grease fitting?     But even the old spring loaded bearing buddies would be pumped until full with extra grease in reserve.  Now those were sealed on both sides of bearing pack.

This is correct. Our employee that deals with bearings for the last 45 years did his schooling and was trained by SKF. He gets called in to deal with bearing failures and solve bearing problems in foundries, automotive plants and other industrial settings. One major reason for bearing failure ( other than no grease) packing the bearing full of grease. 

Either or,   My helmet has been dropped and is way too old, but it’s comfy and is fine.   there is a jump off point where replacing it or not won’t matter.    

Thats an interesting perspective from a Millwrights trade. As  mechanic (heavy truck and coach, automotive I was taught to pack the grease from the large side of the bearing  and fill the aera between the race and roller untill it comes out the other end of the cage.  Put grese in the hub cavity  but not too much. These are tapereded roller bearings , Im thinking in an industrial application a roller bearing may require less. Im not sure how the bearing company comes up with the amount that they give you in a kit. Anybody that had  a Cat in the late 90s early 2000 probably had a front drive bearing failure at low miles, Roller bearing , my Cat dealer told me Arctic cat put out a tender on bearing supply, they did not specify that there had to be grease in them,Was either very little or none! We had a Dexter axle fail where the grease passge  was drilled  near the spindle. It had been cracked for a while , and then let go.

I get rid of helmets every 5 yrs,    motorcycle, snowmobile and bicycle.   Do I need to?   Probably not.   But sweat and oils seep into the styrofoam and deteriorate it over time.   All these Snell, DOT and ECE ratings are only for a 3' vertical drop, it has nothing to do with a high speed impact.   You smack your head into a tree even at low speed that helmet will not be doing much for you.   At higher speed it just makes  it easier for the cops to identify you.   I've got no issue with someone else using a 10yr old helmet.....I just like wasting money.....lol