I am posting this because I feel like it warranted it considering that there is some confusion as to just how long Luffy sustained his G4 form, when he fought against Doflamingo....
Chapter 783 - Doflamingo tells Luffy about the one hour time limit, and explicitly states that after 30 minutes, the Birdcage is going to start "Killing people"
Quote : "Within 30 minutes the dead will begin to amount somewhere or another"
Immediately afterwards, Luffy enters into G4 mode....
Chapter 784: We get a few pages of whats going on around Dressrosa, and the rest of the chapter is Luffy going beast mode in G4....
Chapter 785: On the 8th pages of the chapter, we get to the scene where it says "20 minutes after, and in that first panel, someone is yelling "Watch out, it cuts" <-----This indicates the Birdcage has started cutting people down....
That entire page coincides with what Doflamingo stated during chapter 783, when he said, "After 30 minutes, the dead will begin to amount somewhere or another"
So this is the breakdown.... From the time Luffy first went into G4 mode, to the time that Doflamingo revealed awakening, 10 minutes had passed. Then we get a little bubble that says "20 Minutes after" and the scene that takes place is that of the people of Dressrosa are starting to get cut down. That is the 30 minute Marker Doflamingo was speaking of in Chapter 783....
Chapter 786 - Luffy and Doflamingo continue to fight for a awhile, and after Luffy depletes all of his Haki, he then tells Gats he will need 10 minutes to recover enough for a final attack, but there is only 9 minutes left until the Birdcage kills everyone on Dressrosa.... We know this because....
(Remember, the time frame from when Luffy first entered into G4, till when the Birdcage was going to kill everyone on the Island, was one hour)
Chapter 787 - At the end of the Chapter it says there is only 3 minutes left until the Birdcage Kills everyone on the Island, and there is 4 minutes left until Luffy recovers his Haki. So that means there is a minute difference between the time Luffy stopped being in G4, and the time it will take for the Birdcage to kill everyone on the Island. 9 Minutes until the Birdcage kills everyone, and 10 minutes until Luffy recovers his haki. That means Luffy spent 51 minutes in G4 mode... (Keep in mind Luffy was not at 100 percent)
Luffy enters into G4 mode when Doflamingo says "In one hour everyone on Dressrosa will be killed"
Luffy exits G4 Mode 9 minutes before everyone on Dressrosa in about to be killed
Therefore 51 minutes have passed since Luffy entered G4 mode, and when it wore off....
Chapter 783 - Doflamingo tells Luffy about the one hour time limit, and explicitly states that after 30 minutes, the Birdcage is going to start "Killing people"
Quote : "Within 30 minutes the dead will begin to amount somewhere or another"
Immediately afterwards, Luffy enters into G4 mode....
Chapter 784: We get a few pages of whats going on around Dressrosa, and the rest of the chapter is Luffy going beast mode in G4....
Chapter 785: On the 8th pages of the chapter, we get to the scene where it says "20 minutes after, and in that first panel, someone is yelling "Watch out, it cuts" <-----This indicates the Birdcage has started cutting people down....
That entire page coincides with what Doflamingo stated during chapter 783, when he said, "After 30 minutes, the dead will begin to amount somewhere or another"
So this is the breakdown.... From the time Luffy first went into G4 mode, to the time that Doflamingo revealed awakening, 10 minutes had passed. Then we get a little bubble that says "20 Minutes after" and the scene that takes place is that of the people of Dressrosa are starting to get cut down. That is the 30 minute Marker Doflamingo was speaking of in Chapter 783....
Chapter 786 - Luffy and Doflamingo continue to fight for a awhile, and after Luffy depletes all of his Haki, he then tells Gats he will need 10 minutes to recover enough for a final attack, but there is only 9 minutes left until the Birdcage kills everyone on Dressrosa.... We know this because....
(Remember, the time frame from when Luffy first entered into G4, till when the Birdcage was going to kill everyone on the Island, was one hour)
Chapter 787 - At the end of the Chapter it says there is only 3 minutes left until the Birdcage Kills everyone on the Island, and there is 4 minutes left until Luffy recovers his Haki. So that means there is a minute difference between the time Luffy stopped being in G4, and the time it will take for the Birdcage to kill everyone on the Island. 9 Minutes until the Birdcage kills everyone, and 10 minutes until Luffy recovers his haki. That means Luffy spent 51 minutes in G4 mode... (Keep in mind Luffy was not at 100 percent)
Luffy enters into G4 mode when Doflamingo says "In one hour everyone on Dressrosa will be killed"
Luffy exits G4 Mode 9 minutes before everyone on Dressrosa in about to be killed
Therefore 51 minutes have passed since Luffy entered G4 mode, and when it wore off....