if he goes there. It will take about 4 years minimum for him to wear out his welcome, especially if he wins a NC during one of those 4 years and he is good enough IMO to make that happen at a school like Michigan.
Michigan will still play like they are coached by him for 3 years after he leaves -- just using Stanford as a refernece. The sum is at least 7 years where Michigan will go back to playing quality football.
Holtz only had an 11 year run at ND. I think most of the men on this site would cut off their left nut to get 7 to 9 years of quality coaching again at ND before we die.