Once you have offers, and are trying to decide between firms (hopefully!), you should ask whether they want people to strive to become partners, and if that is the sort of dedication they're looking for.
If they want people who, from their first summer with the firm, to say, "my goal is to make partner!" then they may turn out to be a firm that does not value their associates as much. The result of this may be grueling hours, and your years as an associate may be a trial, trying to weed out those not fit to make partner.
If, however, a firm values their associates for the necessary work they do, and not necessarily because they can repeat the mantra of "I want to make partner" you may end up much happier there whether your goal is to pay off debt, get in house, or actually make partner.
Ultimately, the best way to distill the truth about a firm's quality of life is to get at it indirectly by asking question like the above that may clue you in to things. Another good question to ask of associates and partners alike is what activities, charities, boards, etc. they are involved in. The more activities and social life associates have, the more balanced their workload likely is.