(a) Duration. A sex offender has a continuing obligation to register and keep the registration current (except when the sex offender is in custody or civilly committed) for the following periods of time:

(1) 15 years, if the offender is a tier I sex offender;

(2) 25 years, if the offender is a tier II sex offender; and

(3) The life of the offender, if the offender is a tier III sex offender.

(b) Commencement. The registration period begins to run:

(1) When a sex offender is released from imprisonment following conviction for the offense giving rise to the registration requirement, including in cases in which the term of imprisonment is based wholly or in part on the sex offender's conviction for another offense; or

(2) If the sex offender is not sentenced to imprisonment, when the sex offender is sentenced for the offense giving rise to the registration requirement.

(c) Reduction. If a tier I sex offender has maintained for 10 years a clean record, as described in 34 U.S.C. 20915(b)(1), the period for which the sex offender must register and keep the registration current under paragraph (a) of this section is reduced by 5 years. If a tier III sex offender required to register on the basis of a juvenile delinquency adjudication has maintained a clean record, as described in 34 U.S.C. 20915(b)(1), for 25 years, the period for which the sex offender must register and keep the registration current under paragraph (a) of this section is reduced to the period for which the clean record has been maintained.