Many thanks for all the details, and your theory makes sense. Unfortunately, turning off the automatic updates has made hardly any difference at all for me. Maybe my battery is too knackered by now because of all the abuse it had to suffer and just is not up to the task any more...
It is a pity though, because I love just about everything else about my S3 Frontier.
I had the same problem for months after the update but I can report that my problem is solved.
Here in the Netherlands, Samsung has a Facebook messenger option. I submitted my issue and they promptly answered. After asking the standard questions (reset, factory reset, pairing with other phone, etc) they gave me the option to have it picked up for service. The very next day a courier swung by and picked it up in a sealed container. 3 days later, I received notice that it had been repaired and be delivered by the same courier, free of charge.
Upon receiving my Gear, I really wasn't thinking it would be repaired by was proven very wrong. The motherboard and battery were replaced and also given a software update.
The watch is working perfectly ever since. Long battery life (3 days easy!). Can now sleep with it on to monitor my sleep and also during my workouts.
It came off the charger this morning at 8:30am and still has 99% battery left.
My guess is that there could be a faulty component on the board that only presented itself through the software update everyone is talking about. That would also explain my bluetooth connection issue I was having with my phone and Harmon Kardon bluetooth speaker. It was having dropouts while also connected with the Gear. That problem is also solved with this repair.
Hope this all helps!!!
I thought that probably I have a power-hungry app installed, did a reset, install only trusted apps I have been using for a long time, and everything seemed fine again, battery lasts three days. I thought at the time that the issue had been resolved.
However, a few days later, the same thing happens again... and again... and again... ever more frequently... it seems to happen particularly after episodes of the watch having lost BlueTooth Connection to the phone, e.g. because of having been in airplane mode -- I travel a lot. On a side note, I also have the BlueTooth reconnection issue that is being dealt with in a different thread, and may or may not be related.