The damage is minor. In most cases the real damage to the wood is caused by moisture or dry rot. In the rare places where the ants excavate healthy wood, the effects are localized. It is not unusual to see a few carpenter ants in the home during the spring. They are just scouts from outdoors.
Carpenter ants come from outside in the spring and summer looking for food.
A large number of ants around a garbage can or dishwasher can be explained as an outdoor colony coming in for food. But seeing numerous ants every day in a bedroom, for example, suggests an indoor colony. If any of these conditions exists in your home, you should try to control the colony. The secret to carpenter ant control indoors is to find the nest. If you cannot find the nest, your chance for long-term success is minimal.