They will be much the tastiest if cooked the day of, but here is how you reduce the baking time to 1 hour:

Cook Bake or boil) and slice the potatoes the day before, package air tight and refrigerate. When you are ready to make the casseroles, butter the pans, shake a little parmesan over the butter if you are using cheese.
I always grate some onion into the layers of potatoes.
Make the sauce the day before or the day of, but MAKE SURE it is hot when poured over the potatoes. Put your crumbs or cheese on top, and bake about 1 hour until bubbly. They will be yum!

Or use several large crockpots and a crockpot recipe, but remember to use only canned evaporated milk of cream of something soup; fresh milk will curdle.