(1) A worker's preferred worker certification lasts for thirty-six consecutive months of employment at medically approved work, and will not be extended. The thirty-six consecutive month period begins the first date the certified preferred worker actually returns to work at a medically approved job, but ends no later than five years after claim closure.

(2) The department may interrupt the certification period if medical documentation shows the worker is unable to work due to the industrial injury or occupational disease in:

(a) The open claim in which preferred worker certification was granted; or

(b) A new, accepted claim for a condition or conditions sustained while performing medically approved work as a certified preferred worker.

(3) If the department interrupts the certification period, and when the worker is again able to work, the certification period will resume.