Except for reasons of health, satisfactory evidence of which shall be furnished to the commissioners of pilotage when requested, no licensed pilot or apprentice shall discontinue to act as such nor absent himself at any time from the port and harbor to which he may belong for any period of time whatsoever without first obtaining the permission of the group of pilots with whom he is associated or some duly authorized official of that group, and no such permitted discontinuance or absence for a period of more than one month shall be valid without additionally obtaining in advance the written authorization of the commissioners of pilotage. Any pilot or apprentice neglecting or refusing to comply with such requirement as to his presence and performance of duties in the port to which he belongs, may have, respectively, his license or his apprenticeship, as the case may be, either suspended or revoked by the commissioners of pilotage, depending on their judgment of the circumstances.