Unfortunately, everything is dependent upon your specific state. Each state has its own requirements. We live in Minnesota, which is a very easy and quick state to complete readoption with an IR-3. From start to finish, our process only took 3 weeks, with another 30 days waiting on a new birth certificate. Please check with your agency, as they likely have specific information about your state's requirements. I also found this link to state-specific adoption laws that might be helpful:
http://www.law.cornell.edu/topics/Table_Adoption.htm