I've done both. 

It depends on the program and how much they expect from you. "Top level" can mean and vary a great deal in the type of work and by association the amount of work. 

Admittedly, it all takes time. You need to learn a lot in a short period of time (6 v 8 semesters?). Software, history/precedents, concepts/theory (?), and the possible exterior influences that interest you. That doesn't mean you will need to do all nighters all the time. It does mean you need to be organized, looking at the semester and not just what is due next week.

Most importantly, it depends on YOUR commitment.

In most programs it will vary from day to day how you spend your time in studio.  Some days will have some all-studio meeting time to explain assignments and for the professor(s) to present content - sometimes this may occupy several hours and other days it might take 15 minutes and the rest will be work time.  Some days it will be mostly desk crits - people working individually and the professor(s) making the rounds.  Some days there will be informal pin-ups, sometimes with only a sub-set of the students, and other days there will be long all-studio pin-ups that may take all or nearly all of the 5 hours.  Periodically there will be more formal crits, with guest critics - depending on the school and the studio that might happen only once or twice per semester, or as much as every week or two.

If you're very concerned about schedule - perhaps because you have or are planning to have a job, or be a commuter, or you have a family - then you will want to talk with some current students at that program to find out more about the norms at that particular school and program.  There are some schools where official course hours are pretty well adhered to - i.e. if your schedule says studio is from 12:30 to 5:30 then everybody is going to pack up and leave at 5:30, people won't stand for anything running late, and the space might even be scheduled for some other class on the dot of 5:30.  But it's more typical in a lot of programs that crits routinely run hours over their scheduled end times, and where the general expectation is that everyone - students, faculty, and guest critics alike - are in it for the long haul, sometimes long into the evening.

My experience wasn't one of frequent all-nighters or truly impossible workload - but the time commitment was far more than in an undergrad academic major.  At least 4 days a week I spent +/- 12 hours per day in class or in the studio, and there were frequent related weekend site trips and other demands.  I did have a part-time job in a firm during that time, and was a teaching assistant most semesters.  I was able to take care of myself, get sleep and exercise, but not so much time for cooking...

it depends on many things...

I was a TA during grad school, which obviously meant I had to sit in during classes. I also taught three course sections during the week. 

There really isnt a “normal” week. When you have a deadline things are hectic. Sometimes you don’t have much going on, pretty common for any student. 

I interned every summer, while I was working on my B.Arch. I definitely have more time for things since graduating. During school, it’s all about time management. 

Studio courses are a combination of what you mentioned