Not having a schedule is OK if it's your PhD and you plan to spend 14 years on the thing, or if you're a programmer working on the next Duke Nukem and we'll ship when we're good and ready. But for almost any kind of real business, you just have to know how long things are going to take, because developing a product costs money.
Joel SpolskyThere's a subtle reason that programmers always want to throw away the code and start over. The reason is that they think the old code is a mess. [...] The reason that they think the old code is a mess is because of a cardinal, fundamental law of programming: It's harder to read code than to write it.
Joel Spolsky