Living in humidity, the fight is against moisture and air. For pre-ground, those one way valves do not add much because the coffee is already done degassing. Get a truly tight container, fill it only with what you will drink in about a week, and stash it in a cool dark cabinet. Split the rest into small freezer bags or jars, press out the air, and freeze them. When you need more, let a portion warm up while still sealed so condensation forms on the outside, not on the grounds. Keep your scoop bone dry and close the lid fast.
