The goal of this thread is to consolidate answers to the inevitable question: "How long does 'product X' last?" Given that caveats galore definitely exist, including driving conditions, how the vehicle is stored, etc., please feel free to post those, too. The more products listed here, the better...let's try to get them all!
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I'll start with what I have learned/experienced.
Paint Sealant: at least 6 months
Glass Sealant: 200 miles of rain driving, using wipers; one full tank of windshield washer fluid
HGG: 1-2 months
Patriot Wax: 1-3 months; garage queens will see on higher end+, while dailies will likely see on the lower end; any extreme conditions can/will change wax longevity
Brilliant Glaze: 1-2 weeks (in good weather)
Some products I'd like to know: Buttery Wax? Trim Coating?