Pears should be picked just before they're ripe, often feeling hard at the time, because of the way they ripen, which is from the inside out. If you leave them on the tree to ripen, the central flesh will already be degrading and rotting. Gourmonde is usually picked late September or October, when you might notice a slight change in colour of the skin, but when they are still hard, and ripening takes place while being stored. Keep them at room temperature, check the ripeness by gently pressing the neck at the top of the fruit. If you want to speed up ripening, put them in a paper bag altogether, but preferably not quite touching each other.