If you have an avocado tree, the ideal way to keep the avocados from ripening is by leaving them on the tree as long as possible. Depending on the region, this might be feasible until January. An avocado won't ripen until harvested -- and if harvested too soon will never properly ripen, maintaining a rubbery texture. If you intend to purchase more avocados than you are ready to use at one time, select hard, unripe avocados, and store them in a manner that discourages ripening.
Empty a vegetable bin in the refrigerator. When storing the avocados, you don't want to store them with ethylene gas-producing produce. Ethylene gas aids in the ripening process. Avocados will also produce ethylene gas.
Place the avocados in the vegetable bin immediately. If you leave the avocados at room temperature or store them in the grocery sack, they will begin to ripen. To discourage ripening, keep the avocados cold.
Remove the avocados from the refrigerator and place them in a paper sack, when you want them to ripen. Place the sack in a kitchen cupboard. The avocado may be ripe within a day or more.