Although every situation is unique and one should speak directly to an advisor, the standard is to maintain all data for AT LEAST seven to ten years. Such things as a will, a power of attorney and other specific documents require permanent storage, but again, an exact answer to your exact situation should be derived from an analysis by a qualified advisor.
DISCLAIMER: All technical information presented is necessarily brief. No final conclusion on these topics should be drawn without further review and consultation. Please be advised that, based on current IRS rules and standards, the information contained herein is not intended to be used, nor can it be used, for the avoidance of any tax penalty assessed by the IRS. No Rendering of Advice: The information contained herein is provided for informational purposes only and is not intended to substitute for obtaining accounting, tax, professional or financial advice from a professional accountant and/or other relevant provider. Copyright, 2012, VonLehman & Co., Inc. All rights reserved.