v1.1 to v1.3 should work, but there seems to be a bug in the migrations that we are investigating right now.
In general, we try to release a major release every quarter and tend to ship a handful of minor bug fixes for a few weeks after each major release.
We recommend being on the latest versions and that's the version we use on ODK Cloud. We also regularly roll out security updates for the operating system and the like.
That said, ODK Cloud has continuous backups and all sorts of systems in place to catch and fix problems if they occur. If you don't have those systems in place, upgrading one month after a major release seems like a reasonable approach.
We announce new releases in the Releases category, See How to receive notifications about a category or topic for how to be emailed when a release is published.).
Your Central home page also has a feed of the latest versions.
