There are a few ways to extend the life of the wick. These tips are handy to know for a survival situation or those on a tight budget. Generally, these tips should only be used if absolutely necessary.
1- You can always make the wick longer. After the wick is burned down or cut off with scissors a number of times it can get too short. The wick can still absorb fuel well, but the flame just doesn't get high enough. One way to extend the wick life is to sew a piece of cloth onto the end of the wick. If possible, choose some cloth that has fiberglass and carbon fibers sewn in.
2- You might also raise the level of the kerosene. One way to do this is to put water into the kerosene tank. The water will drop to the bottom and raise up the kerosene. I would think twice before using this technique. It is only to be used if absolutely necessary.
The best way to extend the wick life is to maintain it properly. This involves doing dry burns at the beginning of the wick life and periodically as tar and soot develop. The best way to destroy a wick is to avoid the dry burn at the beginning and then to allow thick tar to develop that can't be burned off.
There are a number of techniques that keep the wick from getting burned out prematurely. These include burning the wick at the appropriate height, having proper ventilation, and cleaning the wick through a dry burn.