46 CFR § 11.713 - Requirements for maintaining current knowledge of waters to be navigated.
(a) If a first-class pilot has not served over a particular route within the past 60 months, that person's license or MMC endorsement is invalid for that route, and remains invalid until the individual has made one re-familiarization round trip over that route, except as provided in paragraph (b) of this section. Whether this requirement is satisfied or not has no effect on the renewal of other licenses or MMC endorsements. Roundtrips made within the 90-day period preceding renewal will be valid for the duration of the renewed license or MMC endorsement.
(b) For certain long or extended routes, the OCMI may, at his or her discretion, allow the re-familiarization requirement to be satisfied by reviewing appropriate navigation charts, coast pilots tide and current tables, local Notice to Mariners, and any other materials that would provide the pilot with current knowledge of the route. Persons using this method of re-familiarization must certify, when applying for renewal of their license or MMC endorsement, the material they have reviewed and the dates on which this was accomplished. Review within the 90-day period preceding renewal is valid for the duration of the renewed MMC endorsement.