I have experience with multiple offices of MBB consulting. It depends on what you intend for "work-life balance". You can always make space for what you are interested in, but the work is very demanding.
12h per day is considered a good lifestyle in all European offices (9am to 9pm), you are on the client site (either in the same city of your office or in another one) from Monday to Thursday in most offices, in others can be Monday to Friday. Some projects can reach midnight, 1am, 2am or 3am every day easily. I would say the average is 9am to 11pm, with a better lifestyle in north European countries and Australia.
On the bright side, the people are so amazing that you suffer much less the long hours. I've been very lucky and in 3 years my average was 9am to 9pm and only worked 3-4 weekends, 1h max, but I'm considered an exception.
There are also a lot of flexibility programs available if you need more time for yourself or the family, the firm is very supportive on that and it doesn't affect your evaluation