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Just to play devil’s advocate, my experience is that Nexus hubs are not what they once were. I’ve owned a few, starting off with several used ones plucked from eBay, with unknown service history and neglected by me, all performed admirably. Then I got one on a bike I bought brand new I guess maybe 18 months ago, it was skipping crunching to the point of being unusable within 6 months despite anally keeping the cable tension adjusted correctly.
You definitely want your maintenance to be preventative rather than curative on a hub gear I’d say.
I recently serviced my Nexus 8 (red-band) hub after many years (at least 5) of use (plus it came from a fairly neglected Carrera at a bike-project so it wasn't new to me). It wasn't always heavily used, but it was used in all conditions. Overall it was in really good order inside, so I'd be slightly sceptical of the need to service it after just 1000km if it's working without issues.
As the photos show it still had lots of grease and just a touch of rust on the bearings between the innards and the shell. I gave it a dip in some engine oil and added some grease to all the bearings and gears before putting it back together. Running smoothly now.