303 Protectant wasn't made specifically for automotive uses, it was made to be a sunscreen for all kinds of products. I learned about 303 first when I got into kayaking, and it was recommended to use it on your kayaking gear to help prevent it from UV damage.
http://www.303products.com/
People should be aware, too, that the automakers are doing better and better at making this stuff last right from the factory. Gone are the days when dashboards used to split, and the foam underneath get all dry and crumbly. The automakers and their parts suppliers do all kinds of 'validation testing' now, where parts are put into test chambers under extreme heat, cold, humidity, UV exposure, etc., to see how they hold up. Vehicles are also left out in the sun in Arizona, too, to test their UV resistance. Everything from dashboards to seat fabrics to weatherstripping is tested, and over the years better UV inhibitors have been added right into the vinyl that makes the dash board skins, for instance.
In the almost 10 years I've owned my Golf, I have seen no 'weathering' type of damage at all to the car, except for the door panel fabric that has come loose (A4 Golf). VW did a bad job with the foam underneath, which disintegrates, and the fabric separates and sags. I've only applied 303 a few times to the dash, shifter area, and tops of the door panels. For the most part, I just wipe it down and call it good.
Long story short, there really is little to worry about with regards to using special products to extend the life of a car's interior. Just clean it with a mild detergent and call it good.
Leather conditioner is for leather, and probably does little other than oil up your vinyl. Leather will absorb the conditioner, but vinyl won't.
I've also read many anecdotal reports that Armor All is bad because it contains silicone, which harms vinyl and rubber, so that was one reason I went with 303 instead of Armor All.