@The:
1350-1500
What I think about
Dressrosa (700->790-800)
Zou (as Post Dressrosa arc) (790->800-810)
Wano (800-810->860-870)
Whole Cake Island (860-870->920-930)
End of Saga
Kaido Saga
Reverie arc (920-930->960-980)
some arcs (we have alot of stuff like Elbaf, the last Shichi and alot mysteries about the story) (960-980->1100)
Kaido arc (1100->1160-1180)
End of Saga
Some prologue saga for final saga (1160-1180->1230-1250)
Final Saga (1230-1250-> 1350+)
When you break it down like that, you're probably right. The final arc/war of One Piece will probably take two years and equal around 100 chapters.
But I would say that the "Kaido Saga" will probably include Zou and Wano, since we are technically already engaging against Kaido current. Because of Kinemon and Momonosuke's reaction to Kaido's name they are probably involved with him. Plus Zou sounding like "Zoo" is a theory. Might be where the Minkmen are from.