That said, I've got 4 G500s and 3 G502s between home and work. The oldest is about 2 1/2 years old (I'm trusting my memory on that), and the newest is about 1 year old (my personal mouse, replaced the ancient G5 when it went out).
I've never had a 500 series go out on me (other than the G5, and that was almost a decade old). I know you haven't had a great experience with the G600, but it's one of the worse models from Logitech. If you're looking for something with scripting capabilities, LGS is really the only option for mice.