40–50 years for premium vinyl. The material itself doesn't degrade — color fading is the limiting factor, and modern formulations resist UV fade significantly better than older products.
Yes, but it shouldn't need it. If you want to change the color, vinyl can accept exterior acrylic paint. Choose a color equal to or lighter than the original.
Yes. Vinyl is inherently moisture-proof, doesn't corrode in salt air, and is rated for wind speeds up to 110 mph in most premium products.