You’ll notice that we often wrap young white-mould cheeses in a special silver paper, which has tiny perforations in it. This wrapping allows the white mould to continue to grow – and the cheese to continue to mature – even once wrapped.
If you don’t happen to have a cheesemonger nearby, you can also tell the age of a cheese by touch. Give it a bit of a squeeze between your fingers if it is firm and has little give, it’s young; if it yields and has suppleness, then it’s mature. Quite a similar experience to picking an avocado.