I read here where everyone uses silicone for a sealant and adhesive. Another product to consider is,3m 5200 sealant adhesive.
This will not let go in high humidity situations, is totally waterproof. It is meant to be used underwater.
You can find it at Home Depot or most marine supply stores.
Pricey, but will last forever. I will add though, it is a bit harder to work with.
But it is paintable. Something to consider for a perfectionist.