Refilling laser printer toner can get to be expensive. Even if you have the self-refill cartridges, the actual toner refills can run pretty high. If you want to get more life out of your laser printer toner, look into products that you can use to dilute the toner before you refill.
Some of these diluting products can turn one bottle of toner into the equivalent of 10 bottles. They are easy to mix in with you toner refill and will not make you sacrifice any of your print quality. These are available from several manufacturers and can be found easiest on the Internet from ecommerce sites. Don't keep refilling your laser printer toner before you check this stuff out. The cost savings are outstanding.