I don't see the point of that however, I mean it's quite huge as it is in my opinion.. I've never had a level taking up the entire grid, and when I had I used some clever portalling techniques so that it LOOKED like the level went on, but it actually teleported you to a different layer.
But even doing that can be tricky and might cause quite a punch on the performance, it's better to create a new level for the next part if your level is getting rather large, or the loading times will just be pure evil.

EDP Map Editor[2D]