Recently I made a list which counts the days since a group's last comeback (as in a release that has teasers, a music video and live performances in music shows).
You can view it here: https://dbkpop.com/db/longest-girl-gr...
This video has the groups that have more than 365 days since their comeback, and haven't disbanded (yet), thus groups that although they are out of contract but their members insist that they haven't disbanded are in.

From most days to least days, the list is:

After School - First Love
15& - Sugar
f(x) - 4 Walls
Brown Eyed Girls - Brave New World
4Ten - Severely
Wanna.B - Why
Dorothy - Purple Lips (not in video - MV not available)
Spica - Secret Time
Crayon Pop - Doo Doom Chit
Dal Shabet - FRI.SAT.SUN
Girls Girls - Juicy Secret
Ladies' Code - The Rain
Matilda - You Bad! Don't Make Me Cry
S.E.S - Paradise
Hello Venus - Mysterious
Girl's Day - I'll Be Yours
Wassup - Color TV
Bonus Baby - If I Become An Adult
Rubber Soul - Love Is (not in video - MV not available)
T-ara - What's my name?
P.O.P - Catch You
Apple.B - Woochuchu
9MUSES - Love City
Girls' Generation - Holiday
Pristin - We Like
Rania - Beep Beep Beep
Good Day - Rolly
A.De - Laputa (Kiss In The Sky)
Hash Tag - Hue
Playback - Want You To Say
Gate9 - Chemical
Sonamoo - I (knew it)
Hint - Walkie Talkie