Originally Posted by
alhedges
However, one of my friends experienced premature failure on both a Shimano nexus 7 and later 8 speed hub. (On a trek navigator). The failure may have been related to the fact that he road in dusty conditions, or that his bike was pretty heavily loaded, or to some other unusual reason...but it has made me a little leery of conventional 7-8-9 speed hubs. (Although not the rohloff; I think you could use that to drive a car).
The fact that your friend broke two different brands would suggest that his requirements regarding coping with his own strength and the loads he expects to carry are probably too high for the low priced multi geared hubs that he tried. I say 'low priced' in contrast to the Rohlhoff beast that seems to cope with anything. These hubs may not have perfect sealing, but I'd be very surprised if the problems were caused by dusty conditions. The lubrication around the seals would surely pick up most of the dust that could get in and stop it going right inside.
Jur's remarks about the small size of the planet gears in the SA 8 speed are worth noting. In the failure he documented, one of the gears actually broke. I have never heard of any such failure in the three speed gear systems, probably because the gears are bigger, but maybe there are other issues relating to low gear ratios creating much increased torque inside the hub. I don't feel certain about the ground here, but I'd really like to know a lot more about these kinds of problems. It would be great to get some really good engineer's report into the capabilities of different hubs regarding longevity, lubrication, power transmission capabilities and general durability.