GM makes a silicone emulsion designed to extend the life of weatherstripping. It's on display at my dealership. I'll grab a P/N the next time I am in there if I remember.
I recently started using 303 Aerospace protectent on everything, Supposedly the best stuff going as far as protecting plastic, vinyl, rubber ect. from UV light and other bad stuff. I like it on tires too. leaves them nice and satin black without a greasy look. Available at www.properautocare.com
Race Glaze Trim & Leather Renewer does an excellent job of dressing and protecting rubber, vinyl, plastic, and leather.
Gives surface a new look (not greasy), anti-static,
pleasant mild vanilla fragrance.
Rich Warner