Very true - it is part of the bane of take home assignments. Even for someone who can code extremely fast, a lot of the exams aren't realistic with time, and then they are compared with those done by people who put in multiples of the asked hours.

I rather put in those extra hours contracting (worst scenario), doing open source work (lots to be done that advances the productivity of tens of thousands of developers, if not more), into my hobbies, or into my friends.