I agree and disagree with this point. The absolute worse thing a startup can do is to "flip"/"redo" their code base, in an attempt to clean it up. We learned that the hard way last year. That said, going through code and occasionally cleaning a class or two in order to achieve a desired feature can save time while debugging, usually a lot.

This is like most things in life, taken in moderation = good for you, but the extreme might kill you (or in this case, your startup).