There is a product that will provide extended protection for polished aluminum. It works! My polishing vendor, who does a lot of bike work, showed me the results of using this on one of his 9 motorcycles. The polished heads on one of his bikes after 6 months looked like they had just been polished by him. He had nothing to gain from telling me this other than to save me money by having him plate some of my polished aluminum parts.
Once I get the time, I will be taking some of my engine components to him for us to use the product on them.
The product is Zoop Seal. It is not cheap but as far as I am concerned is well worth the money. Better than sealing, plating, or continually polishing aluminum components.
Information on the product can be seen at: