The longest time the light could last currently is three days
3 days before the E.coli run out of nutrients, but can't they just give them more nutrients? why is this a problem? Do they produce light 24/7 and die after 3 days because of nutrient depletion?
I'm guessing the light will come with everything intact. You just won't be going back to the labs after every three days to get some nutrient added.
So you need a tiny light ecosystem to renew all the nutrients and resources for the e.coli... that's a pretty neat idea, hard to do, but really cool, keep us updated on this, i would love to get some bioluminescent light for my home
From the sound of it the container probably needs to be pressurized to replicate the conditions of the deep sea or the critters die. If that's the case, opening the container to add food would depressurize it and kill the critters.
Another guess - they would have to be genetically programmed to provide light all the time. I think it might be even more complicated to make them 1st light sensitive then make the sensitivity produce light for the correct condition (when it's light or when it's dark).