Suggest you not wait for them. Instead, get the bearing numbers, go to NTN's site, check with their tech support, and order a new set of bearings directly. When they arrive, "mike" them along with their receivers to make sure you don't have a headstock machining error. With mis-cut threading on (how many?) spindles this sounds like a toolroom QC problem, but at least you'll know that it's not the bearings' fault. With you owning how many(?) of their machines, the response you're getting is kind of strange.