What happens if you don't attend to a critically low stat?

If you ignore a critical stat for too long, you get shut down. If you have a flag, you can use it to save yourself. From my tests on an abandoned Stack Exchange site:

• You can always ignore a critical stat three times.
• You can ignore a critical stat four times, unless something else would cause it to decay faster.
  • A downvote causes Users decay.
  • Low Questions causes Answers decay.
  • High Traffic causes Quality decay.
• You can never ignore a critical stat five times in a row.

If you simply want to be safe, ignore three times. If you are attempting a perfect game, look for situations where you can ignore four times.

It will force you to use a flag, or terminate the game, you cannot ignore them to long. I think the limit is four days, although I don't have tests to back it up.