I would suggest looking for fabrics that are designed for boats. Those fabrics in particular tend to resist to a higher amount of sun exposure and consequently, they should last longer.
There are several manufacturers in the US that carry specific lines focusing on boats and outdoors.
Although most of professionals prefer Sunbrella products, I also suggest you to check the following websites to educate yourself on the options available and decide on which one will be the best fit for your needs.
- Glen Raven, Inc. (Fabrics/Marine) : http://www.glenraven.com
- Specialty Fabrics Review - Buyer's Guide
- Outdura: http://www.outdura.com
Feel free to contact us if you need further recommendations.