Thanks for giving a little more info Jason.
I think we can find out what went wrong if you describe the failure in more detail:
What were you doing when the line snapped, relaunching, jumping, cruising, recovering a collapse?
What was the time between the line snapping and the kite exploding?
Was it an upper or lower bridle line that snapped?
How old were your kites?
About the lines, they are probably good for 60-80kg breaking strength so unless they are worn, damaged or tangled they should not break. Knots will make the line weaker and the loading uneven. It's a really good idea for everyone to inspect the lines on a regular basis.
About the fabric, I talked with Armin, the designer, at Foilfest in Denmark. He said they are using standard "paragliding" fabrics, no extra coating. For paragliders the life expectancy used to be about 300h due to the UV-light breaking down the fabric. A friend of mine in the US was flying an old Airwave glider on which I could easily poke my finger through the top surface, the fabric had the strength and texture of paper!
So if you wanna increase the life span on your foils, don't leave them lying on the beach while waiting for the wind to pick up. Unpack only when you're ready to go, fold it up when you come in for lunch, etc etc... For a $1000 kite and 300h lifespan, that's $3/h when it's just lying there. Maybe the lifespan has gotten better with new fabrics but on the other hand the wing loading is about 3 times higher on a kite than on a paraglider, about 10kg/sqm compared to 3kg/sqm.
If you want to know more about fabric wear, take a look at the links below or do a search on the web.