Those flakes will keep coming. I used the magnet again the other day and got a small but noticeable amount of shavings out of the pot. Personally, I would just strip the chain right away, precisely because I don't want to clean the factory grease off the drivetrain as smelly remarked.
I bought a neodymium magnet with holes and threaded a shoelace through, so I can drag it through the hot wax every couple of months, then just wipe it clean and store it again. I ride up to a couple hundred km a week, my partner much less, and currently rotate 3-4 chains through the pot and found no need to do it any more often than that.
Even so it's a highly optional step, but since I moved away from having a spacer/tray at the bottom of the pot and like to swish the chains around a lot for a good flush and to get the additives in suspension, it's good not to have any of that stuff get back into the chain.