The paperwork which came with the special issuance will spell out what is required and the terms of the special issuance. It may, for example, state that your medical will be valid for six months, and may be re-issued by an AME for a period of two years based on specific documentation.

If in doubt, enlist the assistance of an aviation medical professional who specializes in special issuance. The most oft-recommended here, and by some unions, is AMAS.

The biggest roadblock that delays receipt of special issuance is failure to submit all the required documentation. This results in a series of back-and forth with the FAA as more documentation is requested. This can be minimized by seeking support from medical specialist representation.