Also, I'd like to add that I think this flashback has gone fast because there is just so much story left to tell both in the flashback and the present storyline. There are so many different plot threads going on here, I think Fishman Island is going to be an absolutely massive story arc that very well could surpass Skypiea (66 chapters) as the longest arc so far. I don't know if it'll reach the length of Water Seven / Enies Lobby / post-Enies Lobby which together are like 119 chapters…but we'll see.
--- Update From New Post Merge ---
I also break down the story into larger sagas and individual arcs
EAST BLUE SAGA
-Captain Morgan arc
-Buggy the Clown arc
-Black Cat Pirates arc
-Baratie arc
-Arlong Park arc
-Logue Town arc
BAROQUE WORKS SAGA
-Laboon arc
-Whiskey Peak arc
-Little Garden arc
-Drum arc
-Alabasta arc
SKYPIEA SAGA
-Jaya arc
-Skypiea arc
CP9 SAGA
-Davy Back Fight arc
-Water Seven arc
-Enies Lobby arc
-Post-Enies Lobby arc
THRILLER BARK SAGA
-Thriller Bark arc
PARAMOUNT WAR SAGA (viz title ....but it fits actually lol)
-Sabaody arc
-Amazon Lily arc
-Impel Down arc
-Marineford arc
-Post-War arc
FISHMAN ISLAND SAGA
-Reunion arc
-Fishman Island arc
Not sure if Thriller Bark should be lumped together with the other "Paramount War" arcs or not...it's really the only completely standalone arc so far imo.