How inspiring! I'm sure you will make that 135lbs goal. That is a good question "How to know when to stop?", I have about 10-20lbs to go myself before I start thinking about that.
I'm hoping to start becoming motivated in other ways. The number means a lot to me, and I tend to get upset if I'm working hard and the number doesn't reflect. I think we can all relate to that downward spiral. After I start slowing down, I'm going to try and do some more weight training. I've always loved weights, but when I weight train and try to lose weight, it usually doesn't give me the results I want. I can always gain back muscle without gaining the fat back. That's the way I think of it. Good luck on those next 10-20 pounds!