Substance abuse/chemical dependence is a chronic, progressive, potentially fatal disease. The disease never goes away and can be triggered at anytime without a proper recovery program/plan. It can even be triggered in those with with an excellent program.
The practice of nursing, medicine, law, and any other licensed profession is a privilege, not a right. Because the nurse has access to powerful mood altering substances, a safety net needs to be in place. When a recovering nurse relapses, the consequences are far reaching. One of those consequences is making it difficult for the next recovering nurse to get a job. Five years is definitely not excessive.