Some of the certificates for the Lead-based Paint disciplines contain three expiration dates. The reasoning for this follows.
Interim - 6 Month date set by EPA - According to EPA this sets the interim period for the licensee to work on until you get the license.
OSHA - 1 Year set by OSHA - According to OSHA you must to have annual training if you use Personal Protective Equipment.
Sunset - 3 Year set by EPA - According to the EPA the cert is good for 3 years for use in HUD or child occupied housing.
When the license expires you have to have already received your new license. Encourage the students (licensee) to apply early for the license. It's not like the Asbestos certificates where you have a one year grace period after the expiration date on the cert. With Lead certs once you reach the 3 year date the validity of the certificate sunsets.
For further explaination feel free to contact the U. S. EPA or Seagull.