Are retirement ages for Minnesota Supreme Court justices constitutional?

I recently attended a fundraising party at a downtown Minneapolis law firm. As you probably know fundraisers are sort of like rent parties in college. The host provides some alcohol and snacks and the guests provide some cash for the person or organization seeking the funds. In college one would then try to drink enough alcohol to make attending the rent party a good investment of scarce funds. That sort of behavior is frowned on at fundraisers held at law firms.  So that is one difference between a rent party and a fundraiser.