Comment 8 for bug 544242

An update: Apparently Empathy has switched from using GConf as its settings storage to GSettings and its corresponding dconf. On the first start of Empathy after doing the dist-upgrade, the Empathy settings are imported once from GConf into dconf, and then GConf is no longer used for empathy. Likewise, I imagine that for new 10.10 installs, there never will be a GConf empathy entry.

As such, you cannot use gconf-editor to change the autoaway setting. Instead, you must install the package dconf-tools and use dconf-editor, which works very much like gconf-editor.