We have test files too and I was one of the lucky members of the scholarship committee who got to organize the files this past semester.
Our test files use to be really organized, but with time I guess kinda became messy as people just put their notebooks/papers/tests/quizzes in the files, without actually filing them. Our test files are great and have helped me on many occasions. How we have it is all of the tests and quizzes that people submit are put into filing cabinets and filed alphabetically by class name and number (ie ACCY 201, then ACCY 202, etc...) When we organized these this past semester, I remember finding tests back from 1985, the year I was born. Obviously the older tests and quizzes needed to be thrown away to make room for some of the newer materials.
Then we also kept lecture notes/notebooks/folders/books from certain people if they seemed significant or useful and organized them alphabetically by class also.
I think test files are a great resource for each house as long as you are not doing anything against the rules (such as taking the test when ure not suppose to..). I know I had difficulty in my computer science class so I went to the test files and found a few midterms for past years to use for practice...no they werent the same problems but it was similar and I was then farmiliar with the format of the tests.
I don't believe test files are cheating because I know that even in high school I kept my work and etc for friends I had that were a year younger than me so they could have some direction in the class. My thoughts are: if you have the means by which to help yourself and your friends/sisters/brothers (without stealing tests, etc), then you should do it! Hope that helped