A prenup does not have to be written right before the marriage. You can write it anytime before marriage. In a weird case, if the marriage happens during this 7 day period, then it effectively becomes a postnup, which validity must be reevaluated. Even so, that does not change the community property analysis since it is defined by the act of marriage, not prenup.
The 7 day rule only applies to people without counsel. At least one appellate court does not believe such a rule is required for people represented by counsel. In re Marriage of Caldwell-Fasco and Fasco. For the FB owner, you can be sure he is around with many attorneys
