Right now. There is one important rule in product development: imperfect is good enough. There’s a constant battle between having the product in a presentable state, and having it in a state of perfection.
This will never change, and is one of the reasons why tech companies are constantly brining out updated versions of the same product.
The best products are started in someone’s garage and perfected over time, or dropped without too much investment if they prove unpopular or unfeasible.
A product that is 60% completed but is on the shelves making sales is better than a product that is almost ready, but not open for business because it’s still being refined… and refined… and refined.
So, ask yourself at every milestone, ‘is this good enough to go live?’ If yes, then make it live, and use customer feedback (and sales) to make it better over time.