Comment by SeanBoocock

That can be an asset though, and ideally you want to have both "longitudinal" testing with the same group of testers as well as frequently testing with people who are fresh to the game. The former can reveal trends that the development team is otherwise blind to. It can also help to exercise subtleties of the gameplay that a new player wouldn't discover, or aspects of the "elder game" if the game has a linear progression that takes significant time to unlock.