Recently, Amazon posted an urgent notice about a critical update for Kindle e-readers. If you have a device from 2012 or earlier, then you need to update your software by March 22 — that’s tomorrow — if you want to continue having access to your library, the Kindle store or any other Kindle services on your device.

We know so many of our wisely frugal readers continue to make good use of your old e-readers, or that like so many of us, you’ve passed them down to the kids while upgrading your own. So be sure to double check which device you have, compare it with this list, and be sure to update.

I mean, after a few years, do you even remember whether you own a DX 2nd gen or a 3rd gen? Yeah, neither do we.

The good news is that if you’re reading this post after March 22, it doesn’t seem like you’ll be locked out forever. Amazon suggests you’ll just have to manually install the latest software update for your Kindle device instead.

You can find all the info you need for updating software on this Amazon help page including how to see just which software you’re running currently. And while you’re at it, take a minute to deregister any old devices you don’t use or that you’ve gotten rid of. Just in case.