I change battery, ignition switch, battery Neg cable every 4/5 years whether I need to or not.
Why? I don't like to have problems on the road, kinda like Bruce, rather change when/ where I want to.
Because! EVERYTHING goes thru ignition switch and if you remember the "points" in old distributors, then you know that 5, count them, 5 sets of "points" in the ignition switch look like. They get "burnt" and don't make clean/good connection, ignition switch MUST see 9 Volts for everything to work properly and because we have Multiplex wiring class2, Ground completes the circuit.
Ignition switch sends signal to ECM in millivolts/milliamps, points not making good connection sends wrong signal, now you have problem.
Multiplex wiring send more than one signal in same wire!
This is just what I do, only have 133,000 miles, been to Canada twice.
Dicktator
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4. Neg Bat Cable
5. Neg Bat Cable on Body, glowing from bad connection, Burned out switch, Roof Door Module.