How far in advance of cooking can i peel my potatoes?

One day.

Peel and place into a water solution of 1 gallon of water to one tablespoon of lemon juice or white wine vinegar, then refrigerate till you need them. Drain and cut into chunks, heat (or warm up) then add hot liquids (cream or softened or liquid butter or buttermilk or sour cream) and fold into gently, do not over mix or the potatoes will turn out gummy.