Mine last about a year and half, I wear it everyday, for about 17 hours, I bike, and move around a lot at work as well. I've never had any issues with the stitching coming undone.
It could just be the mind trick thing though--My mother recently told me that I get pretty darn flat with it, which I suppose it relatively true as my binder is able to touch my sternum, but I'm still incredibly self-concious about it, and I hesitate to agree with her.