I suspect that you can put off paying your AMF as long as you would like HOWEVER, you are not permitted to use the certification mark until you do.
your questions are best answered by someone on the management team. This page can provide information and also contacts
https://www.isc2.org/policies-procedures/amfs-overview
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@Sway - please send an email to membersupport@isc2.org so they can better guide you with your inquiry. Thanks!