User blog comment:12th Supernova/Chapter 841: Humanity/@comment-31.24.227.55-20160929165422/@comment-25926617-20160930025532

Luffy could be replenishing with the food that cracker is supplying and then getting a couple of punches in with Gear fourth then eating more so that he doesn't run out like he did against Mingo. I also think the reason why he did it that way was because he thought he could take Mingo out quickly in Gear 4th. Which he did its just the travel time of Luffy flying across Dressroas to get to him was probs not what he was thinking about. For instance if Luffy would ahve hit him a couple times then used King Kong Gun before he passed out he most likely would have won. But he didn't think it was necessary so he waited. In this fight though he knows it will take more than that so he is using it in bursts instead of all at once.

that is just my take on it. Basically what I am saying is stop complaining and wait for the explanation because Luffy might have only used Gear 4th sparingly and then realized he doesn't need it beacuse he only needs to get one punch in with Gear 2nd. There are numerous explanations so be patient.