Really, please back them up. The number of non-trivial apps that now ship with a SQL Server Express backend database is increasing. And that increases the risk that you’ll end up with the one that’s corrupted or broken. Without a good backup there’s no guarantee that your precious data will be recoverable, or that what you can recover will be valid for your application. Having spent a day recovering a SQL Express database that had a couple of corrupted pages in the a datafile, I would like to offer this up to hopefully reduce the number of times I come across this.
Unfortunately SQL Server Express doesn’t come with all the nice functionality of the other SQL Server versions, so implementing backups isn’t as easy as setting up a maintenance plan (not that that’s all you need to do for good backups (See