Shimano Dynamo hub, reliability and bearing life
 

I've been using a shimano DH-3D71 dynamo hub for about a year, and I've been really happy with it. I'm trying to decide whether I should use it for my upcoming pan am tour. I'll be on the road for a year or so, going from Alaska to Argentina.

From what I understand the bearings on one side of the hub cannot be serviced, which concerns me. Is this correct? Should I be worried? Has anyone put 15,000 plus miles on one of these hubs?

I've been using a HB-NX30 Nexus dynamo hub for about eight years, on my commuter bikes. 7200 miles on the current bike, and I'd guess about as many miles on the previous bike (same hub). So far it shows no signs of age.

Why can't the bearings be serviced? I know servicing the old Sturmey Archer dynohubs is a problematic business since you can inadvertently do something really bad to the magnets, but what's the deal with the Nexus hub? I hadn't heard that before.