I've started buying them when they're very hard (Costco sells them by the bag) and then waiting for them to ripen at home. This keeps them from getting bruised by other shoppers. So far, I've had good luck with them being ripe and good for about 3 days.
Yes, this is absolutely the secret to awesome avocados. Buy the unripe ones--the ones shoppers aren't squeezing to death--and let them ripen over a few days. Then, a few days before you run out, go grab the next batch.
