When Should I stop doing cases

As I prepare for the first round of internship interviews with MBB, I've completed around 25 cases with drills. However, I've noticed a significant shift in my mindset and feel that my progress has slowed down considerably. Feedback from previous cases highlights my need to be more concise and improve my calculations.

I have two key questions:

1. How can I ensure I'm ready for any type of case?

2. When should I stop doing cases?

(I often feel like it's an endless journey, and I could have a case that you did not think of it at all, especially since I'll need to do cases again when applying for a full-time position after my internship. I’ve set a goal for myself this year to focus intensely on case practice. How can I that achieve this goal)

Thnaks!