How long does appendicitis last for?

Usually: Gets worsening mid abdominal discomfort over 24 to 48 hours with increasing pains moving into the right lower abdomen, usually associated with nausea, sometimes vomiting and fever.

Until....: Short answer: until you either get operated on or it kills you. Not to say that it's 100% fatal without treatment, but that's how you should think about it.