I thought I would post an experience I had with Meguiar's PP. I had covered my silver 2015 Volvo S60 about a moth ago. I had to skip my weekly wash for 3 weeks on this car and it sat out in what I will call acid rain (not sure if it was exactly that or not.) I finally washed it yesterday.

There was a number of reddish stains throughout the paint and bumpers. After washing with 3D pink soap I was able to get the stains off with a little extra coaxing. While I would say the beading was not all that dramatic, I truly appreciated that this protectant (not sure if I would call it a sealant) kept the stains at bay.

Your mileage may vary.