Always remember that as long as the jewelry does not have any + to skills on it (i.e. stealth, mind, staff etc), it will always provide you it's full benefit, no matter what con it is.
For example, if your ring has +28 dexterity, +20 hps, and +5% heat resists, even at 70% condition it will still give u those benefits. So don't worry about repairing. The only benefits you lose when an item hits 70% con is + to skills.