Yeah, I agree Timken bearings are worth the price. Not so sure about 50 years-- depends if you over-tighten them. I was complaining to racer Vance Breese about how involved the procedure was. Take off the shocks and everything else, tighten the spanner nut until-- what is it-- something like 6 pounds or 9 pounds drag? Vance laughed and said the only way to get an iron Sportster to handle is to find the biggest cheater bar in the shop and tighten the bearing spanner as tight as you can. I pointed out this would egg out the rollers and leave little divets in the outer race, so called "
Brinelling". I found this in a few of the bikes I have taken apart. Vance's attitude was "So what's your point?" In other words, he saw those bearings a frequently-replaceable component. What he was trying to fight was the rear swing arm loading and unloading as the chain pulled on the rear sprocket. He pointed out some racers would even stay on the throttle a bit as they were on maximum brake, since staying on the throttle kept the swing arm pulled to the right by the constant chain tension. He said some guys would get into trouble since if they let off the throttle completely, the swing arm would relax to a neutral position, or worse yet, get pulled left by the 79-and-later disk brake. Then the bike would get squirrly when you got back on the throttle coming out of the turn, since then the swing arm is getting pulled to the right by the chain again.
After that I became a lot less diligent about the assembly procedure. I even own the Chatillion scales needed to pull up on the swingarm and get that drag measurement. Now I just grab the swing arm and tighten until I feel a little resistance to up and down motion. I don't want to dent those races right away, but I don't want a loose swing arm that acts flaky when I power out of a turn.