We've had a few people note wear on their rods, so I wanted to post a how-to on conditioning your rod. Since the rods are a hard anodized aluminum, the hard anodizing process creates a permanent oxide layer on the top of the aluminum. This oxide layer is passive and will not react with normal beer. However if you happen to expose it to a very low pH for a period of time, this layer can weaken. Yeast, water differences, additives, and sanitizers can all change the pH.
The best way to keep the rod in top condition is keep it clean and periodically re-seal it by boiling it in de-ionized water. De-ionized water can be found in aquarium stores for around $0.50/gallon. If you can't get any de-ionized water, a boil in distilled water or in clean tap water with a resistance of greater than 200,000 Ω (measured with a multimeter).
You could also place a very clean rod into the oven at 250º F for an hour or more, and it will use the moisture present in the air to re-seal. Just be aware that if your rod is dirty, that dirt and grime can get baked on.