Tvheadend

I'm currently running tvheadend build 3.4.28 on my old O2 Joggler, via a USB stick which has Xubuntu 14.04 LTS installed.

This build of tvheadend was installed by adding the repository and using: apt-get install tvheadend

I've seen there is a newer build (v3.9.1367) - as mentioned in the updated TvhClient iOS app.

Is this now a stable release, and if so can I upgrade to it, without losing my current setup (recording meta data, schedules, configuration data etc)?

I've had issues previously with tvheadend, when running on my HP Microserver, after attempting a upgrade that left me without a working system. I usually has to start from scratch again and lost all the meta data for recordings.

Is there a recommended method for upgrading releases (or at least a way to backup/restore meta data & configuration settings)?

Is there a more up-to-date stable release than the one I'm running, or are the other builds only beta/unstable builds?

Thanks.