One of the biggest mistakes that people make when using ink refills is using them too late. The key to ink refills is that you need a cartridge that is in good shape. When you let your ink cartridge get all the way down to empty before refilling it, you run the risk of the cartridge head drying out and developing crust or impediments to ink flow.
When you try to use your ink refills at this point, you will see a drastic reduction in print quality. To save yourself from this problem, try using your ink refills when you have some ink left in the cartridge. For the best performance, you will want a consistent flow of ink through the cartridge at all times. You know what can happen to your car engine if you wait too long between oil changes. Ink refills work in very much the same way. Be sure to fill up before you will need to buy a whole new cartridge.