Internal Audit workpaper record retention

Is there a rule guiding how long internal audit workpapers should be retained? If not, what seems to be the acceptable time frame?

Texas retention says 3 years for audit workpapers, 7 years for audit reports.

Missouri is 5 years for all of it.

We use 7 yrs for w/ps and reports. Not sure if it is a mandatory requirement. I do know at the time the decision was made our external auditor was consulted.

Kentucky is 7 years also.

Every state has a different retention period.

KY is 5 years for IA workpapers and 7 years for IA reports.

Audit reports may be permanent, if they are included in either BOD or Audit Committee packets.