I'm doing some experimental batches, trying various combinations. Being fairly new to brewing, I'm not at all sure what makes one beer need to ferment for 2 weeks, another for 4, and another for 6. Or 8. I've brewed from some kits (still extract brewing right now), and the total fermentation time varies, but I've not yet seen the pattern of why & how one chooses that time. Yeast? Malts? Adjuncts? Opinions wanted.