What is the best way to store coffee beans?
Storing coffee in whole bean in the freezer will maintain its freshness for up to a month. It is important to keep the beans in an airtight, light-tight container and return them to the freezer immediately after removing what you need for that serving. This prevents condensation, which quickly erodes the flavor value of the coffee.

If I buy pre-ground coffee and use it up in a week, would there really be any noticeable loss in flavor?
Buying what you need for a week and keeping it stored in an airtight, light-tight container, away from any heat or moisture makes sense because your roaster/coffee purveyor can give you a grind that is more consistent than what most people manage to produce in their home grinder. The large commercial burr grinders (Mahlkoenig) make each granule the same size, which results in a more uniform brew.