You can also refill your other pens as long as you refill it with the same type of ink in there. If you don't know, Google it. I refill my regular permanent Sharpies with black dye ink and alcohol and haven't had to replace near as many as I used to.
To refill, simply pull the nib off the pen gently with a pair of pliers. Some pens you may have to pull the bottom off to refill and some pens you just can't pull anything off. Sorry.
Once you've exposed the barrel, place a few (2-5 drops depending on how dry your pen is) into the barrel and then replace the nib. Store the pen upright so the ink can fully drain into the barrel.
*There may be a splurge of ink coming out the nib the first few times you use it afterwards, so be careful!