The application page says that "Groups that submit early have a significant advantage because we have more time to read their applications." It also says we can edit and resubmit as often as we like. Based on this, we'd be inclined to submit as soon as we've completed all parts of the application to our own minimum standard of satisfaction, then update as needed.
However, I've seen pg say in another HN thread that YC does not reread applications when they are resubmitted, "so submit when you're ready for us to read it the only time we'll read it."
I perceive the trade-off to be that the earlier we submit, the more time YC partners have to read our application and engage with us, but the less time we have to improve the application itself before submitting (better demo, more up-to-date answers, etc). Do pg and the alumni have any advice on this question?
I realize the answer may end up being "you will need to evaluate that tradeoff and decide for yourself."