As far as I know the service interval for the cartridge bearings is 50,000 km.
The number of years between needing service would thus reflect how far you cycle each year.
I tour with mine and it performs well, no obvious drag or problems. Not sure how it copes with total immersion in rivers etc.
Using a modern light system like Supernova E3 Pro front and rear lights gives an always available excellent light for not much weight.
Note that any increase in weight is offset by the lighter weight of your wallet!
Heh-heh! Look superior and say you spent it on German engineering punctilio! The warranty on a SON hub dynamo is five years and nowhere in the information that came with mine (a slip of paper in German about spoking the hub) does it say anything about the bearings being rebuilt at 50K; instead the text implies that it lasts forever if not abused. But 5 years and 50K sounds like a careful match!
BUMM CYO
I've now retired all my big battery lights because they are no longer required; hub dynamo lights are at last good enough. I strongly recommend BUMM's Cyo R Plus as an all-round commuter/touring light; that's the nearfield version; I also have the racer version but it gives you less for the same money in not having the very useful sidethrow of the nearfield and in not having the reflector built in as a safety feature, and in return the racer Cyo doesn't offer you more light or a further throw. The Cyo is better than Volkswagen lights back in the days when they were 6V, and they weren't bad at all. Until a few weeks ago I also recommended the B&M D-Toplight XS Plus for the back but the brand new BUMM Toplight Line Plus is supposedly superior in ensuring one's bike is seen by cars; I'll report when mine arrives and has been tried.
I should add that the Cyo has the best standlight I've ever seen. It uses a capacitor to continue operating the light at about half power and fading away for much, much longer than the four minutes promised in the advertising.
The one I have and recommend is Cyo R Senso Plus, which stands for the nearfield, built-in reflector, automatic switching (for both front and rear lights if you wish), standlight-equipped model, model number B&M Cyo 175QRSNDi. I keep mine on day and night, using it as a daylight running light.
BLINKIES
Though not much use for tourers, who don't want to carry batteries, I supplement my hub dynamo lights with front and rear blinkers day and night. The batteries (2x AA) in the Cateye TL-LD1100 I replace at 100 hours merely as routine; it is supposed to last 200 hours. At the front I use a Polaris L120W (SUNN) blinker that Chainreaction Cycles no longer stocks but which is still sold as a SUNN by Deal Extreme in Hong Kong in both front and rear versions -- I'll get the rear one when my last Cateye breaks (the current Cateye LD1100 isn't my first --- the end cap eventually shakes loose, falls off, and renders the lamp inoperative, which brasses me off as those lights are expensive and should be better made; when you've spent more on Cateye than on BUMM lights it is time to drop Cateye dead). The SUNN light goes about 40 hours on rechargeables, 50h on alkalines; I carry 3x AAA spares.
I recommend blinkies wholeheartedly; I don't think it matters much which you buy any more, as long as you buy strong ones; what matters is to aim them considerately but to use them ruthlessly when drivers don't match your consideration.
With these lights in the lanes, cars visibly slow for my bike. The few who don't volunteer have the blinker, aimed 12 degrees off straight ahead and downwards to a horizon only half a meter high at a hundred meters (the Cyo is set to one meter high at 100m), swept through the passenger cabin by tilting the bike and turning the bars; those drivers volunteer immediately to slow to a safe speed for both of us. Drivers behind me also slow until they can positively identify my bike.
It is an ironic comment on the attitude of drivers that when I wear a luminous Sam Browne and am thus instantly identifiable as a cyclist, they slow less readily than they slow for these lights which they are not used to yet... Fear of damage to their cars is the real motive.
German and Dutch riders should note that blinkies on bikes with hub dynamos are illegal in their home countries.
Hobbes