Kinetic watches are still electronic watches, not mechanical in the analogue sense. Your wrist is converting the winder's movement into electrical energy, thus replacing the battery's duty. Automatic watches wind up a mainspring which stores mechanical energy. The springs weaken over time, the gears wear, the oils dry up. They need servicing. The timespan varies from watch to watch and how it's been worn, as well as the environment it's worn in. Typically, an automatic watch with a high depth rating will have a longer service life than a watch with basic water resistance.
I still really want the black bay bronze, so have put the nomos up for sale. If it goes at asking, then I'll save a bit more and get the bronze. Otherwise I'll just keep hold of it really as it's not worth selling for any less.
Edit*
Been offered a trade + cash for a brand new and unused Halios Seaforth II for my NOMOS. I used to own the Halios Tropik SS back in the day in blue, and that was rather excellent, and sold out almost immediately when it went on sale. It has since been selling for more than retail in the used market in most cases.
ETA 2824-2
Nimbus grey dial
Sapphire crystal bezel (120 clicks)
Superluminova C3 on dial and bezel markers
Brushed stainless steel with polished bevels
Boxed raised sapphire with AR underside coating
Leather + rubber straps included
Really like the look.
I'm waiting to see what the cash addition is on offer before deciding. It means I'll have to add a bit more when I get round to getting a Black Bay Bronze, unless I still like the Seaforth by then, in which case I may just keep that for a bit longer. At least I know that I can sell the Seaforth for at least retail value in the future. It currently sits as "sold out" on Forasec!