There are a lot of "boutique" rubber /vinyl dressings well-respected in the detailing forums, such as Ultima Tire and Trim Guard or Car Pro PERL, but there are also a few very good ones available widely. Meguiar's Ultimate Protectant (also sold as Ultimate Black) is a UV resistant dressing available just about everywhere. Another is 303 Aerospace Protectant, which claims to have a SPF rating of 40. You won't find 303 at Wallyworld, but it's usually stocked at NAPA stores or marine parts dealers.
Make sure the sweeps are cleaned first, so the dressing has a chance to penetrate the rubber. None of these products can reverse the deterioration, but they can sure slow it down and make the rubber look good in the process. No slimy shine like Armorall, just a non-greasy satin finish.
Bill