I just bought a gunmetal gray new car. It stays outside--there's no covered parking at home or at work. So I want to protect the paint to the best of my ability.

Is there any wax/sealant that is known for lasting longer in summer heat and humidity (I live in Mississippi) than others? Or, for that matter, any known to not tolerate heat and humidity that well?

I'm also considering getting the car coated, but detailing my car is the only thing I do for "me time." I hesitate to get the car coated because it would eliminate some of the time I regularly spend working on the car's exterior and decompressing from the work week.