Exam Week Stress

It always seem that at the end of the semester the grades you have worked so hard on the whole year come down to one test. My question is this really fare? is it really necessary for finals to carry so much weight? I feel that if you have shown for four months that you know the material and have learned it then you should not be required to take the final. If this strategy was used then the stress level in students would drop a great deal.