I bought a used ~2012 Bataleon Evil Twin at the end of last season as my first board as I learned. I didn't realize the edges were very dull at the time. I believe it is a park board that would benefit with dull edges when jibbing but at this point I don't need the dull edges. Late last season, conditions were slushy in SoCal mountains so I didn't have any issues with riding it. Now, I am riding it in hardpack/icy conditions (especially at night) and the edges aren't sharp enough to hold an edge. I bought a file guide and ran through the edges many times but the edge was still dull. I then took it into REI to get it sharpened and they improved the sharpness a little but it is still quite dull. If I run my fingernail over the edge, it is no where near sharp enough to scrape any parts off. Is there any way to further sharpen the edges? Is it possible the edge has "ran out" of enough edge material to be sharpened down?