Welcome to the community. I'm not sure if the fish could survive for eight months without food. A fish of 10 years old is certainly an old timer so it wouldn't be unusual for fish to suddenly start behaving strangely. The fact that this fish is 10 years old indicates that it has been looked after properly. Other than its not feeding, how is it behaving? Have you noticed any laboured breathing at all? We always get people to test their water for ammonia, nitrite, nitrate and pH, just to rule our poor water conditions.
What sort of foods have you been giving it? To be quite honest I don't know if there is a lot that we can suggest that will really help your situation. It actually is very common for O's to suddenly go off food, whether they are old or not, the fact that you're at it is very old would lead me to believe age has a lot to do with it.