For every rule of thumb there will be a dozen exceptions. that said 90% of the fish are in 10% of the water, walleye most often hug the bottom and are most active early and late in the day. With a 40 ft lake explore the deep water mid day, but along towards 3pm set up on the edge of a 8/12 ft feeding flat with close access to the deep water,underwater ridges, points and gullies from deep water to shallow flats are major
walleye routes. Most folks quit at sundown, about the time the walleye are moving in to feed. With this tactic your trying to intercept concentrations, sometimes it can be discouraging, you can be a couple 100 feet of route and miss the school. May take a few trys but you hit it and you'll never forget it. I've found some of these routes that have produced for years. When you find one keep it quite, and respect the turf of the other folks you see fishing late. When asked about that limit of lunkers it ain't lying to say they came from deep water!