Wiring in new 13 pin socket

I'm in the process of changing from 2 x 7 pin sockets to the euro 13 pin socket on my wife's estate as a ' just in case situation ' in case the main tow motor develops a problem .

It is a 1989 Citroen BX estate ( diesel ) and I wired up the sockets about 20 years ago and cannot remember why ( age related ) I put all the running lights on one circuit.

Question is :- Should I go to two circuits or carry on with one .

Before you question my sanity , this car does 60 - 70 mpg , nearly 6 feet of load length and will carry a serious weight load.

Michael