(1) Subject to section 75(6), every initial assessment of the extent of a claimant's disablement in respect of occupational deafness shall be a provisional assessment and the period to be taken into account by such an assessment shall be a period of 5 years.

(2) The period to be taken into account by any subsequent reassessment of the extent of the claimant's disablement in respect of occupational deafness, if not limited by reference to the claimant's life, shall be not less than 5 years.