I have a minor problem with the game (Look in bug reports) and I believe the cause of it is that the game tries to render the WHOLE map, I think the game should render the surrounding area, and save areas already rendered (kinda like in Minecraft). Just saying.

It already does do that -- anything far outside of the fog isn't rendered.

As well, the maps aren't unlimited -- they have they're end (30-40 rooms or so)

Yeah this issue has actually been entertained by Regalis on one of the threads a week or two ago. You could probably search for it to see what all was said. (Regalis is the lead programmer/creator of the game)