If I ever get to the point that I think I'll have too much I'll probably first turn it into other build materials like Glass, Stone, Stone Bricks, Half Slabs, Stone Brick Half Slabs, etc. If I ever get enough of those as well I'll probably void the stuff, but for the time being I don't think I'll ever reach that much because I prefer IC2 Miners over BC Quarries. Unless I start hollowing out a giant pit in the ground or something I don't think I'll ever gather so much more than I need that I have to start voiding it.