If you go to the Amazon Kindle forum there are threads on this. It seems someone on the Kindle team made a mistake and forgot to remove the expiration message when it was taken out of beta. They don't know how many versions were effected but it should be fixed now in the new versions.
When I contacted Kindle supported last month. No one knew anything about it. Then I was told it was an "oops" on their part and they were working on a fix. I was using 1.9.3 when it happened. I upgraded to last version before this one and the problem went away.