How can I preserve avocados longer? Avocados are tricky beasts.  If you get them while the peel's still green, they're hard as stones.  When they ripen, the skin goes brown and the flesh softens, but when this happens you have to eat them immediately or they'll start to go bad right away, often ending up full of nasty brown spots within a day or two.

Is there any (relatively simple) way to keep them ripe and still edible for a bit longer?

(In case it makes any difference, I'm talking about ordinary Hass avocados you can buy in pretty much any normal supermarket in the US.)
I haven't done a side-by-side comparison, but I find that once an avocado's ripe, I can keep it there for a few days by putting it in the fridge.

It doesn't halt the process of getting brown spots inside, but it seems to slow it down some.