When I planted kale last fall, I thought it would be a through-the-winter kind of thing. Now the plants are gigantic, and still producing yummy leaves. I snip off budding bits so the kale won't flower and go to seed yet. If I continue this, will these plants just go on forever? Or will they become undesirable in some way? How long can I expect to enjoy these plants? I think they're Red Russian kale.