Longest Comebacks!?

Do you mean the longest amount of time between comebacks? Because if so, you're kind of including weird choices vs. say, Big Bang (Flower Road in March 2018 to Still Life in April 2022) or Jewelry (Sophisticated in August 2009 to Look at Me in October 2012).

Feel Special - More & More is 9 months, longest ever, I search for other groups to watch and got 2

if only group comebacks count then red velvet went 20 months without a comeback. dec 2019 to august 2021.