While they are durable, there is a way to "cake the screen" and reduce the functionality big time. You want to avoid EVER touching the screen with your fingers. The oil from your hands can clog the screen, especially if it is a fine micron (which is typical of nicer grinders). The same would probably apply to throwing a penny/quarter in the grinder chamber that wasn't fully cleaned. Pretty sure scraping the screen wouldn't help, but if it were to get clogged then some high % iso would do the trick.