Answer:
There are no published hard-and-fast rules about how much documentation is appropriate for exemptions. If it works for your bank to have customers sign such a statement at the time you're entertaining the exemption in the first place, it makes sense to have that statement renewed or confirmed when you review the exemption.
With increased scrutiny on BSA/AML processes and policies, it's usually not a good idea to "back off" on due diligence in any attempt to better KYC.
First published on BankersOnline.com 10/18/04