I brought my GS exactly 1 year ago. I have only worn it for a few special occasions. Apart from that it has sat in a draw. To test it I did not change the time last October. So the watch ran for 1 year with out interruption.
At the year mark it was 4 seconds fast. Up until June it was only running 2.5 seconds fast. Then with the warmer temperatures it sped up slightly.
I set it to Time is and have repeatedly checked it against that.