oldgearheadFrom what I understand, minute particles of the metal are deposited as you write. I can't find the source again, but I think it is actually oxidizing as it is deposited as well, creating what is written.
ABlueWhaleForever is a long time. But it would take a ton of use to abrade away the tip, and given that these are not really ideal writing instruments, you won't use it that much.
ABlueWhaleI think they are saying "ink" because there is no real way to say what is "leaving" the pen and depositing on the paper to leave some writing. I guess they could say it writes with "contact"? For all intents and purposes, it will never run dry because the removal or "decay" of the metal tip is inconsequential in our life times. It won't wear out in other words. I also see a little tongue in cheek saying it will never run dry because it can't, there's no liquid ink to run dry.
ABlueWhaleBasically it's an old fashioned "lead" pencil (when pencils really were made with lead and not graphite), except it uses some other alloy since lead is toxic.