If you look at the voting page, you see that all the ones at the top have been around several months, or even over a year. They've not gotten there by necessarily being more popular, but simply by being around longer. In addition, files that stay around for months at a time clutter up the voting page. An exceptional idea can easily be drowned in the dozens of others.
Both of these problems could be solved by only keeping files open for voting for a specific month. At the end of that, they could no longer be voted on and would be moved to an archived section. The winners of the monthly vote in each category of file would be clearly the most popular, and thus the ones that EMG could give the closest scrutiny to.
Objectivity and an end to clutter, how could these be bad things?