Ceviche should last from 2 to 3 days in the refrigerator depending on the freshness of the Ceviche.
You should however eat the Ceviche within 24 to 48 hours for the best taste and freshness.
After 3 days in the fridge then the Ceviche should be thrown out to avoid getting food poisoning.
If you want to keep the Ceviche longer than 3 days then it should be frozen to keep it longer although it may not taste as good as it did when fresh but it will still be safe to eat as long as it's been frozen if longer than 3 days.