I have seen countless notes on the hard start relay. My understanding is that the wires get old and become more corroded and hence more resistive. More resistance leads to larger voltage drops across the wire and consequently less current. Couple this with the fact that the starter solenoid heat up with use and requires just a little more power.
What I have not been able to determine, is just how much resistance in the wiring is too much. Can someone please quantify this value. In this way, one can determine if this is the actual problem or if something else is occurring.