I ran a 5-day experiment to see how fast Google reshapes your ad profile

Three fresh Google accounts on different US residential proxies. Two browsed with specific personas (fisherman, fitness). The third did nothing for five days.

Google was more aggressive than I expected. 17 new ad interests from a single session. By Day 1 it was already removing interests and replacing them. Not adding to your profile. Rewriting it. The control didn't move once in five days.

I built a Mac app (MirrorMask) that does this against your real profiles. Happy to answer questions about the methodology.