Many shops today will offer rotor replacement as the first option without even measuring the rotor's remaining material. Although there are other reasons besides minimum thickness to condemn a rotor such as rust choking the vented section which reduces airflow and increases the chance of brake fade, and cracks from extreme use, usually a rotor can be re-used for 2-3 wear cycles and machined 2 times. With all that in mind, the Reduce and Reuse concept works perfectly here and may even trigger a positive response from environmentally conscious customers.