To kind of answer your broader question as to how quickly they restock generally, I’d say it’s every few months. There’s no specific schedule for resupplying or anything like that (that I know of at least). I think it depends on how popular the unit is, and when they have a large enough order to their suppliers to get done.
I just wanted to follow up just so you knew it wasn’t something where you’d see your preferred units back in stock within a few days or weeks. It’s typically a while longer than that, from my experience!