Back in the early 1970′s Armorall was introduced and quickly adopted by car owners and others who wanted to keep plastic components looking their best and lasting as long as possible. 303 Aerospace Protectant is the professional-grade version of this kind of product, and I have yet to find anything better.
Predominantly sold to aerospace and marine users, it’s widely available online and at marine supply stores. It does not gloss up plastic, doesn’t leave gummy residue, and actually does work to extend plastic life. The proof for me has come in the fact that I am one of the few owners of a Porsche 924/944/968-series cars whose dash has not cracked over time: my car’s almost 19 years old now and all the treated plastic and rubber components are doing just great.