Yes and those certain conditions will be the plot cause Oda will never explain G5 time limit .
He will never say how long luffy can stay in it or how fast he can get back into it without eating or how much stamina it use etc etc .
It will always be some unknown limit to us that will chnage depending on how Oda wants .
Yes and if Oda wanted to he could have him done it again .
Luffy pushing him self near death over and over has never stop him before .
The G5 Limit doesn’t need explanation because it’s evident in the story? People complain that Oda doesn’t always use Show don’t tell, but now we see that if he doesn’t directly tell people dont understand.
Theres no hard set time for G5 just like there isn’t for G2 or G4 or G3. The time limit is dependent on how many calories Luffy has to burn which is why he needs to eat immediately after to regain the form, to gain more calories and energy to burn with it.
G5 is an insanely taxing form with its damn near infinite regeneration, its increased strength and speed, the increase in size to giant form, and the elasticity and movement in general. That’s why when Luffy showed the power to restart G5 in Wano it was after he ate a full months of food not even an hour ago. Luffy had the excess calories to spare. In Egghead luffy didn’t have that hence why he couldn’t.
Luffy like all people is limited by the amount of energy they have available to them. G5 just is a very taxing form