My late father was a big fan of The Tonight Show until Johnny Carson's departure, after which he gradually lost interest. He always maintained that Steve Allen was the wittiest and best of the late-night hosts; what dad thought about late-night TV after Carson would be pretty much unprintable.
I can still remember being allowed to "stay up late" and watch some of the (post-Tonight) Steve Allen Show episodes. Everyone who came later owed Steve Allen a debt (at least Krusty the Clown admitted it).
I was a little kid in the 80s...it seemed like Ed McMahon was just ubiquitous on television back then - commercials airing during breaks even on shows he was not on during my normal cartoons - probably for those “you may have already won $10 million” envelopes you would get in the mail from Publisher’s Clearinghouse. I can’t really recall seeing The Tonight Show “the first time” staying up, but I do remember it seeming ‘familiar’ simply because of Ed McMahon’s presence. He had such a kind face and caring sounding voice, I guess that’s why as a kid it seemed ‘safe’ to me whenever he was on.