Keep in mind you can do this once a week or more, always testing and tweaking. Finding new ways to make each one better than the previous. So the sooner you get it done, the sooner you can get results and start the next.
Remember my past failure where I wasted 6 months on a product? The good thing about this is you will know right away. If you send 500 people to the landing page and only 5 people register, then you know you need to work on your offer.
But if you send 500 people and 400 register, then you know you struck gold! The best answers you will get will be your own results. Keep plugging away! And test everything before you go live guys.