Ideally, for muscular endurance 15+ reps is sufficient, so going a lot further over that may not be very useful (unless you compete in CrossFit as an example). If you can complete 20-30+ sit-ups ...

CrossFit is a discipline that has gained immense ... correct technique to perform burpees safely and effectively. 2. Sit-Ups: ...

When most people think of a strong core or achieving abs, the first exercise that comes to mind is often sit-ups.