This isn't what usually happens though. If advertising drove negative value to a brand over time it just wouldn't be purchased.

Not many companies can take off purely on the quality of their product, especially in boring industries. I can't think of an insurance company which I learned about outside of widespread advertising.

Assuming you're consciously aware of what's going on. Maybe you are, but you wouldn't know if you aren't. You can't really claim to be immune to subconscious tricks.

The Mere Exposure Effect does work though, probably more effectively than you realize.