Is there a point after which it is counterproductive to do cases? What's the ideal number of cases that I should practice before I should stop? Thank you!
Number of cases
This is a great question, I see a lot of advice (even on MBB websites) suggesting you don't want to be over-prepared. Yet I think many of us who successfully get in end up studying well north of 50 to 70 hours; I spent well over 100 hours for example. Can you succeed with less? Sure, but why risk it? You will only have so many opportunities to apply: After undergrad, after you masters, and perhaps once or may be twice as an experienced hire.
Based on my experience, the most important factor is not the number of cases, but the time you spend getting ready: both how many hours (cf. 50+ hours above) and the number of days / weeks you allocate. I started preparing slowly a few months before I even applied, and really intensified it the last month. The last few weeks, I'd spend 2 or 3 hours a day practicing.
I believe there's one more thing that's extremely important beyond the time you spend studying or the number of cases you go though: the quality of your feedback. I just finished writing the below on another thread, and it is very applicable I believe so bear with me as I do a simple copy/paste:
My recommendation is such: do a (couple of) case(s) with a current/former consultant early on, and write down their feedback; practice on your own and with fellow applicants and work on the initial feedback; mid-way through your prep, perhaps do another case with a consultant to course-correct. Near the end, do one or two more cases w/ a consultant to make last-minute adjustments. All throughout, do 15-20 minutes of mental math and market sizing every day. Total prep time should be well above 50 hours over 4-6 weeks, don't hesitate to go over 100 hours like I did.
Look, I know some of you may think I am just talking my book and trying to convince you to spend money - no, I am not. I was lucky to have 5 friends at BCG when I applied, and each one of them gave me at least 2 cases (for free). But if I had not had these friends and had just studied on my own, odds are I wouldn't have made it, plain and simple. If you are in school, you probably have access to alumni or upper classmen/women who have at least done an internship and would be willing to help for free. If you do cannot find someone to help you, my honest opinion is, get ready to spend some money. Yes you can get in without this - but the odds would be stacked against you. It is a competition, spots are limited - and we always have a lot more qualified applicants than openings. Luck plays a role, but might as well be as prepared as possible -> At the end of the day, nothing can replace the feedback one of us current/former consultant can give you.
The short answer is: if you've solved 30-40 cases succesfully in a way you felt good about your performance, you are ready. Longer answer: I've personally struggled with this while prepping myself. Here's what I've realized: the moment you notice you are not excited about the prospect of solving a case, one of two things have happened: (1) you have done enough practice but not really improved and are disheartened by the prospect of struggling again or (2) you are doing fine, but your brain is just too tired to handle another mentally exhaustive case.
Doing cases is a bit like gym -- a mental gym if you will. The first few weeks shows no improvement - mostly fatigue. By the end of 2-3 weeks, you are getting stronger, lifting longer, running faster. You are excited to get up and hit the gym again. And by week 5-6 you are plateuing out and your body needs down time to recuperate and be excited by the prospect of gymming again.
You need to sit down and think hard about whether your fatigue is because you haven't really improved, or because you have improved a lot but now plateued. If it's the former, talk to a specialist - a professional who can pin-point the major weak areas you need to focus on. If the latter, take a week off, go out, meet people, relax. You won't forget how to solve a case - trust me. Come back in a week and pick a tough case. See how you do.
short answer - yeah. after you've done 100, other than the bare minimum to stay sharp there isn't much point... its just going to stress you out