how much air is in a vacuum bag with whole beans? you think whole beans will stay fresher or pre ground beans will stay fresher? have you tried coffee from a bag that was roasted more than a month ago and compared it to one that was roasted a week ago? vacuums aren't perfect and preground coffee makes it worse. i dont read italian. thanks for linking that article. there is no such thing as manufacture specified optimal grind size. there's an optimal espresso (with the right color, flavor, and crema) with many variables that go into it. individual tamping pressure for one is a big variable and the only way to accommodate for it is by changing grind size. some people tamp harder meaning the espresso will tend to be overextracted. you compensate by increasing the grind size so theres less surface area for water to interact with.