The NRA American Rifleman Dope Bag Staff did the Marlin Goose Gun test.
They attached a choke and fired the gun for pattern and velocity, then cut off one inch, reattached the choke and tested again.
They continued to cut off in one inch increments until they were down to 12 inches.
Anything that's going to happen ballistically in a shotgun barrel happens within about 18 inches.
The only advantage of a longer barrel is that it points better.
Anything over 28 inches and you actually start to loose velocity due to friction.
Barrel length has zero effect on patterns. An 18 inch barrel will pattern as well as a 36 inch.
Things didn't "Start to get out of hand" until it was down to about 12 inches.
The idea that a longer barrel will shoot farther or "harder" is a left over from the days of black powder when a longer barrel burned the powder more effectively.