Nope, that's where save states come into play :) just write a save state, you can turn your computer off, then you can just reload the save state and keep playing. The save state "freezes" the game, similar to closing your DS lid. And 400% is rather slow :\ so it will probably take a long time. I get to 1000% and it took me what, two weeks to get that spread? Try and get it to 600% at least..