I am looking at a used 2000 Honda Insight and I am a bit hesitant to buy because it has 120,000 miles. So that's one answer for you: it lasts at least 120K. However, my concern is how much longer it may last. Any Insight owners with high mileage or who have replaced batteries? I haven't been able to find anyone yet, which is a good sign. And FYI, the replacement cost for the Insight from the dealership is $3000 including labor.