Well, I don’t think there’s much point in discussing the requirements… I suppose the requirements are given.
However, if the requirement is strictly no internet connection, it should be ensured by a firewall - not by trying to configure the application not to do so and then assuming that if it conforms over a short period of time, it will conform always.

As I said previously, avast! will [try to] connect to the internet in certain situations, and I don’t think there’s any way to prevent those attempts.