First off, the battery time thingy is always not really accurate, second, you might be running RAM-eating apps at the time, so it might be telling you how much time you'll have RUNNING those apps for a long time.
I am really dumb, sorry, there IS a S-Voice option on the phone. But not on the gear. I tried it, but it did not work, it didn't bring up anything. AND on the Applications list on the Gear Manager, I saw S-Voice! But still, not on the gear...
That happened to me before, and I just did a factory reset. It worked, at least. If you don't mind losing your data, go to recovery mode, then select the factory reset option.