Notwithstanding subdivision (a) of Section 18901, the department may authorize the retention of eligibles on an employment list for an indefinite period of time based on the following factors:
(a) The number of names remaining on the list in relation to the anticipated number of vacancies.
(b) The qualifications of the eligibles.
(c) The gender, ethnic, and disability composition of the eligibles remaining on the list.
(d) The lack of unreasonable denial of a competitive opportunity for potential applicants.
(e) The availability of alternative appointment options.
(f) The modifications that have been made in the duties, responsibilities, and qualifications in the class specifications since the establishment of the eligible list.