I stepped up a starter once and it overflowed. Since then, I put a towel under my stirplate and won't make more than 1000 mL at a time. I make my starter the weekend before I brew. When it's finished I put it in a 2 liter pop bottle and keep it in the fridge. If I need more than a liter, I just make a second starter then put it in the same pop bottle. I usually decant some liquid before I add the second starter and I always decant before I pitch.