This will vary by student, number of classes enrolled in, number of clubs active in, recruiting schedule, and Career Services workshop options.
Classes are usually held one per week for three hours, with an average of 5-8 hours of out-of-class work per class. You can take 3-5 classes per quarter. Class work will take about 30-50 hours per week. BUT, these are averages and some people can get by with skipping classes and only studying a few hours per week. Many more have very thorough study regiments consisting of group study sessions after the assignments are completed. So it's really up to you how much time you decide to dedicate to classes.
Clubs throw lots of breakfasts, lunches, and social events that you can attend for 0-20 hours per week. Totally optional, but I'd argue that these interactions just as important as the classes.
Recruiting is brutal, but not everyone participates in the same way. Aspiring bankers and consultants have it rough from the third week of the quarter on. Dozens of firms throw events (with attendance sheets) every day so you can find yourself attending four events in one day, ending with a handful of business cards that you need to write follow-up emails to. If you're really good, you'll start getting invited to dinners and mixer events with specific firms. These will add another 3 hours after the other events. An aspiring consultant myself, I'd say that I've spent about 30 hours on average attending these functions. It sounds like a lot of work, but these can actually be a lot of fun. You just need to enjoy talking with people.
Next on the time-taking list is Career Services. This team is amazing. They have dissected the entire recruiting process and designed a curriculum of 1-3 hour sessions (mostly optional) that thoroughly explore each particular area, going into details such as "How to write a follow-up email to a recruiter" or "Exit strategies when leaving a crop circle." These are really helpful to those who are unfamiliar with recruiting. Expect one or two of these each week.
With all of the options to chose from, you will often find yourself double-booked and need to prioritize or compromise. But remember that classes are the only mandatory part of this program, so you can take it really easy if you want. My advice is to keep a very detailed mobile calendar, add every event that you may want to attend, then participate in as many as your endurance will allow. And don't even think about skipping TNDC.