Report Abuse. It really depends on the ripeness of the avocado as it comes from the store. Some stores put a sign on avocados that are ripe and ready to use. Gently press the bottom of the fruit and if it yields, its ripe. Rock-hard avocados can take anywhere from 2-3 days to ripen.Putting them in a bowl with other fruit, or in a paper bag, will hasten the process.mtngigi · 6 years ago.ome stores put a sign on avocados that are ripe and ready to use. Gently press the bottom of the fruit and if it yields, its ripe. Rock-hard avocados can take anywhere from 2-3 days to ripen. Putting them in a bowl with other fruit, or in a paper bag, will hasten the process. mtngigi · 6 years ago.