And consider yourself lucky if it is only sometimes! My typical week as an associate, get in at 8, leave at 10, half day Saturday. I did however get to fly on the Concorde when I was a second year associate coming back from Stockholm through London. Was also able to bill more than 24 hours that day (we billed for travel time back then) because of the time zone changes and getting back to NYC before I left London.
I am with @L_NewEngland that undergrad does matter, but in this case Duke, Columbia, and Dartmouth are equivalent. Where will you be happiest and therefore make the best grades? That is the question you should be asking.