That's why I'm going to bring 2 calculators into the exam. A few people have changed their casio's battery after 2 - 4 years. I guess it just depends on how often you use it.I have a casio.
But wait, how come my casio has never had to have a battery change? I've had it for over 3 years now. What if it dies in the middle of my HSC? How long do the batteries last haha?