I have a request to automatically have a plan end and convert to 2nd plan at the end of 5 years

I have been asked to configure a retiree life plan so that when the retiree has been enrolled in it for five years that it automatically converts to a second plan with lesser coverage. I haven't had much luck with configurations to get this accomplished and may have to create a custom program. Anyone who has had a similar request please let me know how you handled this.