As the words Whole time Director itself says that such director will appoint for whole time. In the Companires Act, 1956 there is no specific period given for the WTD as given for MD.
If whole time director is appointed under schedule XIII then the tenure would be as per schedule XIII i.e. 3 or 5 years and accordingly he may be reappointed for such terms.
Part I of Schedule XIII of the Companies Act, 1956 deal with appointment of WTD which not defined the period for which a WTD will appoint, it generaly says the condition which will be complied for appointment.
But part II of Schedule XIII specified the limits of tenure. Therefore, according to the remuneration of the WTD, the tenure would also to be decided as per Schedule XIII.
However, in case the appointment does not fall in part II, the WTD may be appointed for whole time as Mr. Ajay said above.
Kindly appreciate Whole time word has nothing to do with life time appointment. These words denotes the amount of time one has to devote for a company.
As law is silent regarding tenure So keeping in view the industry norms i would advise you to appoint WTD for a period of 5 years. Further if the appointment is in accordance with Schedule XIII then observe the advise of Ankur Srivastave sir...