Light is everything in Salem. Each lantern throws a radius of warm ward that turns wandering spirits aside, so the shape of your lit streets is the shape of your safety. Spirit-lanterns and shadow-lanterns ward harder than a plain brazier.
Think in coverage, not count. A dozen lanterns clustered in the square leave the edges dark for a Shade to walk; the same dozen spread along your homes keep everyone safe.
TIP Over-light before storm and Mist nights. The fog eats your radius, so what is plenty on a clear night is thin in the murk.