When you enter polish mode, you hunker down.

You don't add functionality to the product, you just add robustness and polish.

When it feels like you're 80% of the way done, you're actually 20% of the way done.

If your goal is to have a perfectly polished thing, you'll spend most of the effort on polish.

You'll lock in whatever fundamentals you had quickly gotten in place.

If the product is complex, it will take time to polish all of it.

That means that you lock yourself in place, and it could be up to a year to get it out to market.

If the market is moving quickly, by the time you launch, you'll have a year-old product.

In a fast-moving environment, big-feature sets with high polish aren't viable.