That's complete fucking bullshit, humalog is good for months in the fridge, there is no way it would start crystalizing, it sounds like the guy had a bad batch or something...sounds more like a quality control issue. The standard protocol for humalog cartridges is to keep one cartridge in the pen for everyday use (which you will get a week or few out of) while you keep the rest of the box stored in the fridge.