As of December 1, 2015 Michigan law was amended to require that the training for a CPL application be provided within 5 years preceding the date of application.
The law also requires that all certificates issued on or after December 1, 2015 must contain the expiration date of that certification.
If you took your training before that date, you can still use the certificate as long as the date was within 5 years of the date of application.
Prior to this amendment, there was no expiration date for the training certificates, and every county clerk handled the issue differently. Some required the certificate be within 6 months, some never considered them expired.