I couldn’t find a good link online explaining this, but I’ve had a lot of luck keeping avocados in the refrigerator.
The trick is to let them ripen on their own until they’re about good enough to use. If you put them in the fridge, they can keep about 1-2 weeks there at the same ripeness before they start to get softer or ripen further. That’s contra leaving them on the counter, where they’d be ripe enough to eat for a few days.
Ooh, I never thought of this. Thanks for the idea.