I think that would depend on where you are doing your surgery sub-i's at. I'm a fourth year student at UCLA applying for general surgery, and chose to do my sub-i's at the main UCLA hospital. I think by far the UCLA surgery 3rd year clerkship is quite tame compared to other medical schools. Some people would get slammed at the county hospitals if they were assigned to trauma services or general surgical services, but it was not uncommon to hear my classmates getting done by 3-4pm without any call duties at the main UCLA hospital. It was equally not uncommon to hear residents who came from other medical schools telling us we have it way too easy. Since I wanted to do surgery before I hit my 3rd year surgery clerkship, I stepped it up a notch, came in early, stayed late, took extra patients - all the stuff you already know you should be doing in a clerkship you're interested in.
When it came time to do sub-i's, I pretty much applied the same principle as I did during my 3rd year clerkship, volunteering extra call, taking extra patients, helping the intern with floorwork on all of the patients on the service, anticipating what work needed to be done and getting it done before I was asked to do it etc. I know the expectation was raised during 4th year, as I got more pimp questions during rounds, clinics, O.R. but that didn't come as much of a surprise. I did more than 80 hours a week during my time there, but as you assumed, I also assume we aren't complaining about the extra work because this is the field we want to do. In the end, it didn't feel like I was doing a ton of extra work when comparing the sub-i to the 3rd year rotation. I dont think that was a definite answer, but maybe it might give you some insight.
