Hi everyone, I am drawing about 1-2 hours per day with Staedtler Mars Lumograph pencils, and I'm going through them so fast! I bought an extender because they've become short in about 2 months, but I'm wondering if this is normal or if it has to do with the way I'm sharpening them (General's handheld cheap red sharpener) or the way I'm drawing with them or what? I'm too lazy to sharpen with straight blades - is this a big mistake? Can you recommend a better sharpener? If it matters, I have a lot of those little sharpeners, so I don't think the blades are bad.