the only way to make them last is to pull the internal assemply out regulary (easy and fast!) and regrease the whole lot especially the needle bearings.
i have to take the above statement back...because i just remembered somebody on a forum saying that you can replace the lubrication (grease) in a shimano 8 speed internal gear hub with an oil bath (automatic transmiission fluid)...
the oil gets splashed around nicely and penetrates all parts constantly...lubricating and cooling everything...
here is an example (from 'hubstripping.com') of how to do it:
"bob carter
November 26, 2008 at 10:40 pm
Hi ‘Urb’
my ‘oil cap’ was just a short M5 posi screw with an o ring under it. You just have to avoid the races inside the outer casing, drill & tap ( don’t tighten the screw up too much either….) Yes, a long screw would foul the innards of the hub, there’s not much clearance!
The axle bearings are not sealed so if you tip the bike over all the oil will run out – just something to be continually aware of!!!"
http://hubstripping.wordpress.com/alfine-shimano/
and i think this is the site where he shows how he put an oil port in:
http://dr2chase.wordpress.com/2010/12/23/how-to-put-an-oil-port-into-an-internally-geared-hub/
the trick is the right amount of oil...too much and it gets squeezed out the seals that are not made for oil lubrication...too little and it does not get to all the parts...
here is somebody else (hubstripping.com) who had problems with the needle bearings and cages i mentioned above:
"Konstantin
February 27, 2011 at 3:57 pm
Those who consider changing the lubrication for an Alfine 8-speed might want to know that the planetary gears in the carrier unit run on tiny needle bearings – with rollers of around 1mm, and packed in some plastic cages.
I have a 2 year old hub (SG-S500 “B” type) destroyed by water ingress (IIRC it had only 4th and 8th speed in the end) so I took it apart to see what’s wrong, can it be cleaned/fixed, and how it works in general, and discovered the above. In my case, some of the rollers were shortened by rust – and in the process of rusting the rollers also partially destroyed those plastic cages. I de-rusted them chemically (Fertan gas tank rust treatment) after which I saw some of the rollers shorter than the other. I am not sure they’d last any significant amount of time if I’d try to re-use them, in particular – the cages..."
more from 'hubstripping':
"Aaron Goss
March 8, 2011 at 4:35 pm
...Oil Baths are exactly what needle bearings need. Grease is used on the gears to prevent wear and on the ball bearings to fill up the spaces and prevent water entry."
