Steve, pretty good info you have gotten so far.
Much depends on how dry the air is in your part of Kansas. Our winter air is rather dry here, well so is our summer air..which is the point, locally you will have differences. I think much moisture in the soil is lost to the air -vs- leaf transpiration in winter. What I do is wait until I see the soil starting to pull away from the walls of the pots, if you have mulch on top then this may vary. When the soil has pulled away about and 1/8-1/4" and I can scratch into the soil about 1/2" with my finger and I can't feel any moisture at all, then I water. I prefer to put about 2" of snow on top of the soil of each plant, if there isn't snow I use ice cubes like you mentioned but I try have about half the surface area of the soil covered with cubes. My smaller pots(0.5-2gal) that are up high on shelves get 2-4 loosely packed snowballs the size of tennis balls gently lofted up(like very carefully shootin hoops), bigger ones get 4 and smaller ones get 2...you get the idea; as far as ice cubes these pots get about a 8-10oz cup full for the smaller ones and 16oz for the bigger. By the way a dust pan is the perfect tool for distributing snow from the bank to the pots. For me the timing works out on average to be every 3-4 weeks, but sometimes later in the winter it will be more like 2 weeks here. If you can scratch a bit into the soil and feel any moisture at all, don't water.