Hi Boon Siong,
Your JNCIE-M remains in the 'Active' status for 24 months from the date of certification. If nothing is done to recertify during this time frame, your JNCIE-M moves to the 'Inactive' status for 12 months. You can recertify to the Service Provider track by earning the JNCIP-SP anytime during this 36 month period.
However, if nothing is done to recertify during the Active or Inactive periods, your certification moves to the Expired status. Certifications in the Expired status cannot be renewed. You would have to start at the beginning of the Service Provider track.
You can find more information about the new certification statuses on our website at http://www.juniper.net/us/en/training/certification/already-certified/recertification/.
Regards,