Whenever the retirement board, pursuant to examination by the board's physician and such other evidence as it may require, shall find a firefighter has been disabled while in the performance of his or her duties it shall declare the firefighter inactive. For a period of six months from the time of the disability the firefighter shall draw from the pension fund a disability allowance equal to his or her basic monthly salary and, in addition, shall be provided with medical, hospital and nursing care as long as the disability exists. The board may, at its discretion, elect to reimburse the firefighter who is disabled for premiums the firefighter has paid for medical insurance that supplements medicare, including premiums the firefighter has paid for medicare part B coverage. If the board finds at the expiration of six months that the firefighter is unable to return to and perform his or her duties, the firefighter shall be retired at a monthly sum equal to fifty percent of the amount of his or her basic salary at any time thereafter attached to the rank which he or she held at the date of retirement: PROVIDED, That where, at the time of retirement hereafter for disability under this section, the firefighter has served honorably for a period of more than twenty-five years as a member, in any capacity of the regularly constituted fire department of a municipality, the firefighter shall have his or her pension payable under this section increased by two percent of his or her basic salary per year for each full year of additional service to a maximum of five additional years.