It depends what the state in question defines as a sex offender. Some might argue that once you complete, you are complete. While others may view you as never done. Case in point, what is a 10 year offense in Pa, might be a lifetime offense in another state. In Ny, the same offense that put me on the registry in Pa for 10 years, put me on the registry for 25 years in NY, because NY does not have a 10 or 15 year option.
The best way to not have to worry about it would be to apply (and receive) a full Pardon for the Pa Governor. They are EXTREMELY difficult to get.