The electrical impulses sent through the Buick Spark Plug Wires should be at a consistent level for a period of five tune ups. After that point, the spark plug wires will begin to show signs of wear which will include an increase in resistance to the transfer of electrical current to the spark plugs.
In the past the spark plug wires had a copper wire core that was strong and consistent. The use of glass fiber cores is what is being installed on vehicle today from the Buick factory because they have been shown to have an even smaller amount of resistance to the flow of the electrical current through them than the older style copper core.
On about the fifth tune-up your Buick has is the correct time interval for the replacement of the spark plug wires so the resistance of the old wires will no longer increase to the point of negatively affecting the performance of your engine. If this is not done on time, the spark plug will be receiving a reduced amount of electrical voltage and could foul out.
Another reason for replacing the spark plug wires is when the end that connects to the spark plug becomes disengaged. This can happen when the wire is pulled instead of the boot at the end. In time the boot will become slightly fused to the spark plug. By twisting the boot slightly before the pulling process begins, it can disengage the boot from the plug keeping the Buick spark plug wire intact. If the wire is disconnected from the boot then a replacement set will have to install on your Buick. This is one electrical device that should not be attempted to be repaired.