[QUOTE=njtug;60065]Why does the dangerous liquids class expire in 4 years?[/QUOTE]
See 46 CFR 13.209:
Each applicant for an original “Tankerman-PIC” endorsement shall present a certificate of completion from a course in DL or LG appropriate for tankships and for the endorsement applied for, and approved by the Commandant. The date of the certificate may [U]not be more than 5 years earlier than the date of application[/U]. [emphasis added]
The course is given in the junior year, thus it is valid for four years after graduation.