Sometimes you can add stuff to the resin to make it last longer.
In most cases, carbon fibre (aftermarket stuff and stuff you can buy off the shelf) will begin to disintegrate 12 months or so after it's made if it's left in direct sunlight (IE: a car parked on the street). This lifespan can be dramatically increased if your car doesn't see the sun much
Cars with carbon panels USUALLY have the panels painted. Or they are toys that don't see much sun.
The only reason i'm saying this is because I was a part of a team at uni that was experimenting with CF for the SAE racecar. Works fine for a race application, just don't expect longevity.