NVC process for I601A waiver filers; HELP!

[Brazil2USA2016 7]

My I130 was approved on February 3rd. I received an email from NVC (Nationals Visa Center). It stated that they will now be processing my case. The email states that I need to pay certain fees. It also gives a list of documents that need to be submitted.  I will eventually be submitting the I601A waiver, but not for at least 6 months.

My question: Do I pay and submit all of these documents PRIOR to submitting the I601A? Or do I wait until it's been approved (which could be 18 months from now)? The email states that the fees/documents will expire after one year. I don't expect to have an approved I601A within one year. Should I wait?

[p-ana 933]

From what I understand, you will have to go through everything, even interview, to have your case denied and be given the option to apply for the waiver.