IB in the US - how many days off per year on average?

I did banking for 4 years, most recently with one of the top bulge brackets firm before moving to VC. I would say you are in for a rude awakening if you think you will be able to take more than 2 weeks vacation at the most especially the first year. Even then you will be tied to your blackberry and be expected to respond (and even do considerable work) on your existing projects.

Now sure, every banking group is different, you will learn that not everyone works as long hours and some groups are more brutal than others (i.e. you can't expect someone from Equity Capital Markets to work as much as someone in M&A or Financial Sponsors). I personally worked for one of those brutal groups so my experience may be different than others. Than again most bschool students glow at the idea of doing M&A or working with LBO clients and these are exactly the type of groups I am talking about.

I used to tell people - make sure you do banking for the right reasons - interest in global markets, passion for finance, exposure to landscape changing decision-making, etc. instead of doing banking for the money. If you do banking for the wrong reasons, you will not last. However over time I think I've changed my mind - the people that survive this industry and stay for the long haul are the ones that money defines who they are and what they stand for, their place in life and society. The ones that love the job but decide no price can justify the lifestyle, these people move on to other more forgiving careers in terms of hours.

I've had this conversation with many people and for most there is no way to understand until you try banking. My only advice would be to go in there with your eyes wide open and really understand what this is worth to you. I think banking is a great place to start and looking back I would probably still do it all over again, but it's by no means the type of job that a sane person does for the long haul.

And I don't want to burst any bubbles for anyone but I think some of the "perks" need to really be evaluated in context.
- Dinner allowances are great if you would rather spend your Friday nights having dinner in the conference room with the analysts instead of a hot date. Also $20-$25 allowance won't buy you a steak dinner every night, not sure what part of the US that's possible
- Black Car service is definitely enjoyable at 4am in the morning when the only thing you wish is that you stupid driver would pick up the pace that is costing you an extra 10 min of lost sleep. In the satellite offices (SF, LA) where black cars are not used analysts / asssociates frequently crash their cars falling asleep at the wheel. Just ask any "friendly" banker from Merrill Lynch San Fran to tell you about the tally of their junior bankers (analysts+associates) that have crashed their cars in the past year alone. I think they even have awards for it!
- First class flights - sure let's take the typical business banking trip in context - take red eye flight to arrive at xxx destination in the morning for the 9am meeting. Spend most of the night on the flight working on presentation, model, etc. Arrive at xxxx location at 7am. Check into the 25-star hotel that you will probably see for no more than 2-3 hours during the entire trip. Run to business meeting half asleep. Get through meeting. Go to another meeting or work at a business center until hours before your flight back home. Swing by 25-star hotel room to pick up your stuff. Luckily you never had time to unpack anything since you barely stopped by so all is good. Catch red eye back home. Spend majority of night working on some other upcoming presentation for the meeting in 2 days. Arrive back to home city just in time to catch your lovely black car back to the office in time for some more work. Contemplate pulling a gun on the driver and making him drive off the bridge to end misery. Then suddenly remember you are one of the most risk adverse people in the world (after all that's why you joined banking) and suicide definitely involves some risk. Put idea to rest. Arrive back to office and prepare to do the above over and over and over and then one more time again

P.S. And guys please understand life does not get considerably better once you get above the analyst / associate role. Sure you won't be spending 100 hours a week being a monkey and crunching numbers or putting together pretty slides anymore. But you will be spending these 100 hours from red-eye to red-eye from visiting one client to another, going to never-ending diligence sessions, conferences etc. Your work-hours won't change considerably - the only thing that will is the type of work you will be doing. I like to think of it as being the true investment banking monkey during analyst & associate years and then moving towards more of a mgmt consulting lifestyle once you reach more senior levels (i.e. constant traveling from place to place mainly on red-eye flights. This is true to such an extent that they even have a name for when a non-MD takes a day-time flight. They say "Wow, How did you manage to get on the MD flight?")