The worn spots in the first photo wlouldn't phase me at all. But those paint cracks? Time for a new stem. Life's too short to be spending it wondering each ride if this is the one. (Says a poster who didn't do that wondering when he was young and paid big-time.)

My policy, simple - replace stems and handlebars before they break. You are doing that. Good work.

Edit: Apparently that is not Timothy H's policy.

Ben