The consensus is that it is better to buy coffee beans than ground coffee. The ground coffee will already have leaked flavour, and will lose more, rapidly, once the pack is opened. But that, with vacuum-sealed coffee, is not my experience. I cannot claim to have done exhaustive tests; but I have found that the ground coffee is more flavoursome than the beans. Why, I have no idea.
I keep it in the freezer -- again, not recommended by coffee lovers, who point to the moist atmosphere of freezer compartments. I screw up the bag, and put the bag inside a jar with a tight lid. This protection seems to work fine.