Petitioners insist that they should be considered regular employees, since they have rendered services which are usually necessary and desirable to the business of their employer, and that they have rendered more than twenty (20) years of service. While this may be true, the Brent  case has, however, held that there are certain forms of employment which also require the performance of usual and desirable functions and which exceed one year but do not necessarily attain regular employment status under Article 280.  Overseas workers including seafarers fall under this type of employment which are governed by the mutual agreements of the parties.               In this jurisdiction and as clearly stated in the Coyoca case, Filipino seamen are governed by the Rules and Regulations of the POEA.  The Standard Employment Contract governing the employment of All Filipino Seamen on Board Ocean-Going Vessels of the POEA, particularly in Part I, Sec. C specifically provides that the contract of seamen shall be for a fixed period.  And in no case should the contract of seamen be longer than 12 months.  It reads:               Section C.  Duration of Contract               The period of employment shall be for a fixed period but in no case to exceed 12 months and shall be stated in the Crew Contract. Any extension of the Contract period shall be subject to the mutual consent of the parties.               Moreover, it is an accepted maritime industry practice that employment of seafarers are for a fixed period only.  Constrained by the nature of their employment which is quite peculiar and unique in itself, it is for the mutual interest of both the seafarer and the employer why the employment status must be contractual only or for a certain period of time.  Seafarers spend most of their time at sea and understandably, they can not stay for a long and an indefinite period of time at sea.  Limited access to shore society during the employment will have an adverse impact on the seafarer.  The national, cultural and lingual diversity among the crew during the COE is a reality that necessitates the limitation of its period.               Petitioners make much of the fact that they have been continually re-hired or their contracts renewed before the contracts expired (which has admittedly been going on for twenty (20) years).  By such circumstance they claim to have acquired regular status with all the rights and benefits appurtenant to it.               Such contention is untenable.  Undeniably, this circumstance of continuous re-hiring was dictated by practical considerations that experienced crew members are more preferred.  Petitioners were only given priority or preference because of their experience and qualifications but this does not detract the fact that herein petitioners are contractual employees.  They can not be considered regular employees. x x x[18]