On a related note, one of the things I like most about Everdo is the way it stores data. Everything is in an Sqlite database, on your machine.
So in a way, everything is already archived and can be kept forever in a timeless way. Just make sure to backup the DB file once in a while.
The Everdo database file can also be read by other apps and scripts to generate any kind of report one wants. This requires some programming skills, but it’s powerful.