You can renew up to 6 months before or after your renewal date. If you pass your renewal date you can still login to the Jeweler Site and renew!
You can even login to the Jeweler Site (within 6 months of becoming an inactive Jeweler) to renew your contract with Premier Designs! When you do that, your next renewal date is updated to a full year form the day you renew, so that you receive a full 12 months for $350.
If you do not renew within 6 months of becoming inactive then you will need to begin again as a new Jeweler.