Someone sent in a question to The Jewish Ethicist about his working long hours in a law firm. R. Dr. Asher Meir responded:
What then is a "standard" work day in a place where there is no custom to extend it? The Talmud tells us that it begins at daybreak, and continues until some time before nightfall, in order to allow the workers to arrive home before dark. (On Shabbat eve the worker needs time to make minimal Shabbat preparations before sundown, so he must leave earlier.) (2)In other words, "Don't complain. Historically speaking, until recently everyone worked long hours.
It's clear that this is quite a long workday nearly 12 hours on average. Certainly this is not customary today, though in some professions, including yours, 70 hour work weeks are not too unusual.
However, he adds that we must dedicate a certain part of the day to learning Torah and that the obligations on a worker should be clearly delineated.