@Kaido:
I don't think he was in Gear Fourth at all past that initial usage, and he had Nami and the homies to protect him in that case. Otherwise he just ate Cracker's biscuits, and it seems unlikely he'd be in Gear Fourth to do that. That's how the anime interpreted it at least and it seemed pretty accurate. No way he was constantly in Gear Fourth for 11 hours, especially given the hit-and-run strategy he developed later on.
With some tenacity, I'm sure Luffy can find a way to keep himself in the game with Katakuri, just like he did with Cracker. Gear Fourth can only be a last resort, especially when he's alone.
I'm sure it was said fight, eat, run. So there was fighting too, not just eating. And I don't really see nami and baum protecting him every 20 minutes for 11 hours.
These days it doesn't look like g4 can be last resort anymore considering g3 and g2 did bad with cracker, doflamingo, katakuri. It's clear these gears are outdated and can't handle the strong pirates anymore. He pretty much needs to start with g4, talk about when he will face the yonkous.
Then again, it was implied the time limit is based on the haki, so everyone should have that time limit and weakness if they use their CoA too much.