Or torn out a single segment and them opened another portal, thereby creating two portals in the Nether and another whole portal worth of obsidian... that's just my experience with portals from many many months ago, though.
You're exactly right - as long as the portal was rebuilt far enough away (or take down the first portal), it's literally a way of generating more (obsidian) blocks in the world.
Or work with a friend, have that person take out the portal's nether entrance, then just restart the normal portal = boom, 14 more bricks.
