Do Proportioning Valves Wear Out?

Does the sermon count for church this morning...lol?

Thank you Redfish, I appreciate your candor. Actually, from the 75 Dart donor car I've acquired the upper control arm, spindle, rotor, caliper dust shield, hoses and proportioning valve. I'm planning on replacing the hoses and wasn't sure about the prop valve.
As you might have noticed, I'm a novice mechanic with much to learn. Subsequently, I've decided to let my mechanic do this job precisely for the reason you opened you reply with......."it's brakes". I don't want that nagging feeling in the back of my mind as I'm cruising "did I put everything where it belongs"?
At this point in the project, I want to hand off all of the parts necessary for him to complete the job.