One of the most common questions I am asked is how much time is needed to prepare for case interviews? My response is typically extensive preparation gives you an enormous advantage.
The ratio is probably 15:1 or 20:1 in favor of the person who prepares a lot vs. someone who prepares little.
Now for some people, the situation is unavoidable. They apply to MBB, have no idea what the industry is about, much to their surprise get an interview, and then for the next 72 hours they are Googling "what is management consulting."
Someone in this kind of situation is a little bit out of luck.
But there are also quite a few people who are much earlier in the process. Perhaps this is you, and your likely interview dates are weeks or months away.
Assuming this situation describes you, you have a very important decision to make.
Do you prepare now for the case without knowing if you will get an interview? Or do you wait until you know you have an interview, and then start preparing?
The real problem is one of lead time.
From the moment you get a call from a recruiter saying they would like to interview you to the time you actually need to show up for the interview is typically 3 - 7 days.
In theory, it would be smarter to wait until you know you have an interview, and then start to prepare. The problem is:
1) you don't end up having enough time to do a great job, and
2) you're competing against people who started preparing months ago.
They enter the first round doing their 51st case. You enter your first round doing you first case. It takes an awful lot of talent to compensate for such a major disadvantage.
The alternative isn't great either. Perhaps you decide to prepare in advance, and then you risk doing all this work and possibly not even getting the interview!
So yes, the timing tradeoffs in this critical decision pretty much stink.
Basically, the key is to pick the decision that stinks the least for you and your situation.
Pick the decision you would least likely regret later.
The scenario you want to try to avoid is doing preparation half way.
I get a lot of emails from people who did not put the time into preparation, did so as a conscious and informed choice, lined up interviews with six firms and then promptly get rejected from five of them.
In a moment of shear panic, I get the email that says they realized they under-prepared, they've decided to fight back and commit deeply to getting good at cases before the interview with the 6th firm, they work like crazy, and then get the offer from the 6th firm.
This is cutting it kind of close don't you think.
In the end, this person ends up practicing just as much as everyone else who gets an offer, but everyone else gets multiple chances to perform at their best (perhaps they prepare really well before interviewing with the first of six firms), meanwhile your back is against the wall and you only have one shot to get it right....
Dude, that is a lot of pressure.
You just need to ask yourself if working in consulting is something you are deeply committed to or not.
If you are going to be deeply committed, then it pays to be deeply committed early.
Because deep commitment late in the process is the same amount of work with much lower likelihood of success.
It is awfully difficult to perform perfectly on every single case, every single time.
I mean when I interviewed, I had about 61 case questions of which I only passed 60 of them. My sole rejection was from BCG in Round 1. And for what it is worth, it still bothers me to this day! And to add insult to injury, it was just an estimation question, not even a full blown case.
I think I did make some moderate level mistakes on another case, but the interviewer passed me anyway -- mostly because his colleagues all thought I was pretty good, so I think he gave me the benefit of the doubt.
For that case in particular -- I was jet lagged (three time zones), only slept four hours, was very tired, not thinking at 100%, and missed something small but significant in the very unusual case.
Give yourself some breathing room to allow some margin for error.
And quite ironically, when you know you have some margin for error, you're able to relax, and you end up performing a lot better than having only one shot.
Another observation on this point, when I get emails from people with offers from MBB - McKinsey, Bain & BCG.... 50% of the time, the person got an offer from only one of the top three (+ an offer from another Top 10 firm).
35% of the time, they get an offer from two out of the top three firms.
And 15% of the time they get an offer from all three of the Top 3 firms.
Phrased differently, 85% of those who end up working at McKinsey, Bain or BCG made a "mistake" somewhere in their recruiting efforts that did not allow them to get offers from all three firms.
In other words, 85% of the "winners" had done extremely poorly at least on one occasion.
It is very hard to be perfect.
The key is: give yourself as many opportunities as possible after you have thoroughly prepared.
Avoid deciding to prepare after you get rejected from all but one of the firms you are interviewing with.
The timing of when you prepared has a very high leverage impact on your recruiting results. The timing of the preparation is very 80/20.
Some people say that the most talented people are the ones who end up getting the offers.
There is some truth to that statement.
But there is also truth to the statement that the offers go to the people who are most deeply committed to getting an offer (and by extension are the ones whose commitment takes the form of extensive preparation time).
While I think both statements are true, I think most people overestimate the importance of talent and under-estimate the importance of deep commitment/preparation.