That's not what I mean. I'm not using the term "working software" as "great project success". I mean it as something executable that you can develop, test, and get feedback on.

The software will be slow and buggy and do the wrong thing. If you find this out in month 1, then that's great. If you start with 2 months of careful planning to make sure you don't get it wrong, you'll find out it's wrong in month 3.