The purpose of the Desire Statement is to support you in giving attention, energy and focus to your newly birthed desire. It teaches you how to language desires so they feel good. The key tothe Desire Statement is it needs to be TRUE for you. You'll notice that one of the recommended sentences is "I love how it feels knowing...." Using this sentence allows you to state your desire in a way that makes it true for you. When it is true for you, you send out a positive vibration. It's not a matter of how often you read or say your Desire Statement each day. Your goal is to give your desire positive attention, knowing that as you do that you are sending out a positive vibration.
Once you create a Desire Statement, you have completed step 1 and 2 of the three step Law of Attraction formula. Now your work is to Allow. Spend most of your time and energy there. Keep finding proof that you are manifesting something that is in alignment to your desire. When you celebrate and acknowledge something you have manifested, this proof helps remove the doubt and negative vibrations that prevent you from receiving your desire.
In short, it's not about how often you do each step of the Law of Attraction formula. The key point is to send out or offer a positive vibration with respect to your desire. Identify what you want, give positive attention, energy and focus to it, and remove the doubt and negative vibration you may be sending by celebrating proof as you find it.