I'm not sure anyone else on the other side of the argument than you would agree that it is not impractical if we had the will, unless you mean if everyone magically had the will to turn their firearms in at the same time. Of course, if everyone woke up one morning and decided peace and love were the way to go, they could ride their unicorns in to their local police department and hand over all of their guns.
But the reality is that some legal owners of firearms just might turn their stuff in, and most would not. Certainly those with illegally owned firearms would not. At that point you bring up that, over time, the illegal firearms would deteriorate or something and eventually no one would have guns. The real world just doesn't work that way, and even if it did, you're asking folks to disarm themselves and live among criminals for "some period of time" - fat chance. I sure as hell wouldn't do it.