Windshield wipers are just one of those things that get old and needs replacement. You wouldn't want to be in the middle of a bad storm when your wipers fail. However, instead of replacing them every few months, you could just as easily extend their life, while allowing them to work at their peak efficiently. The rubber portion on your wipers will always work best when clean, so it is a good idea to wipe them with denatured alcohol (91%) once a month. You can also use fine sandpaper (1000 to 2000 grit) to do the job. This will keep them flexible and better able to hold to the glass and wipe water and the debris away.
Note: Keep in mind that when it comes time for wiper replacement, you should only need the rubber squeegee; not the entire metal rod. The only time you should need the rod is if it has become severely corroded or bent. However many wipers are designed to be replaced entirely, so you will have to consult with your local automotive specialist to see what options are available.