In the Dayton area, obviously WLW blasts day and night. WCKY is moderate during the day and has a lot of groundwave/skywave cancellation and interference at night. 1360 is weak but audible days, in but with lots of interference at night. 550 is moderate days in Springfield, better in the south suburbs, and moderate at night with some interference (some which shouldnt be there). WDJO on 1160 is listenable until WYLL fades in three hours or so before sunset and is nowhere to be found at night.
In the Lafayette, IN area, WLW is moderate to strong days but suffers a lot of skywave/groundwave cancellation at night, WKRC is barely there under KTLK, and 1530 is weak days and strong nights. Crossville, TN: WLW not there days moderate to strong night, WCKY just blasts in, and I don't remember hearing 550 (though I did hear a weak 1360 and 1160...also Dayton's WING and WONE, the latter after sunrise).
When I lived in Quincy, IL I heard WLW about 1:30pm Central one winter afternoon, otherwise was very strong at night. WCKY was also strong at night.
I was under the impression that WLW (W8XO) never used the 500000 watts in the daytime, in fact much of its use was after midnight.