Now can you please provide data for the maximum 24/7 safe current per 18AWG wire.
My own research led me to believe it is much lower than 9A.
Useful table here
http://www.powerstream.com/Wire_Size.htmusing "The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle."
AWG 18 is okay up to 16A (~<200W @ 12V)