I've a Samsung-based phone where the headset-jack (it has a mic, it's a headset-jack not headphone-jack) has taken years of abuse and still going strong. Jogging with an armband and using it in bed and getting snagged and clipping it to the jogging stroller and subsequently forgetting I was tethered when I step away.... none of that did damage.

My phone is a Samsung Focus, which came out a year before the G-Nex. I'm surprised the G-Nex gave you so much trouble.