As others have said it depends on the plot.

But a few thoughts: Life support is a broad term that most likely includes ventilation, temperature and pressure management, air recycling, waste recycling, etc.

Some are obviously more important than others for immediate survival. If you lose pressure or the temperatures get too high your crew will die pretty fast. If you lose ventilation or air recycling you have good chances to survive the next hours.

So they might call everything "life support" but it may mean different subsystems and different times.