Sec. 6.04. TERMINATION DURING FIRST 2-1/2 YEARS. If, during the first 2-1/2 years of disability retirement, a retiree recovers to the extent that the person is able to perform the duties of the person's job as a firefighter, the board of trustees may terminate the retirement benefit and restore the person to active service at not less than the same rank the person held at the time of disability retirement.