why do electrical wires coil over time?
That happens because of the way most folks coil the extension cord.
If you &quot;roll&quot; it up around your arm, you twist the cable as you coil it around your arm.  Every time you coil it up, the twist gets worse.
If you have an extension cord reel, then you won't get a twisted cord.
You have two options to avoid twisting your extension cords:

Use an extension cord reel to roll up and store your extension cords.
Alternate from which end you coil the extension cord if you coil over your arm.  Roll it up one time from the plug end, and the next time from the other end.  Swap ends every time you roll up the extension cord.