This is normal. When I was scheduling classes I would weight them by difficulty and have a cap for total course weight to account for it. Otherwise it's easy to overload on hard courses.
I certainly tended to do that as an undergraduate when I could. Credit hours or the equivalent correlate pretty loosely to difficulty and the time you'll need to spend. (And, of course it's even truer when you mix in non-engineering classes which aren't necessarily easy but were relatively speaking for me for the most part.)
>On average, I studied for 40 hours a week and completed a course every 3 days.
I will say that when I was in university, there were very few courses I only spent about 24 hours on. In fact, there are probably a fair number of courses which, even had I taken them a couple years earlier, would still have probably taken more time than that to do assignments and brush up for exams.
