An employee who has used all accrued sick leave, together with the additional sick leave provided by this article, and who has used all vacation days to which he or she is entitled, and who is required to be absent from work for an additional period by reason of illness or injury, may be granted a leave of absence, by the Borough Administrator, without pay, for a period not to exceed six months, which may be extended for an additional six months; provided that the granting or refusing of such leave of absence shall be a matter within the discretion of the Borough Administrator based on the Manager's determination as to the quality of service performed by the employee, the length of the employee's service, the effect of such prolonged absence on Borough services, and such other matters as the Borough Administrator may deem relevant to its determination.