Does the + and - connection wires have to stay the same length?

[sternwake]

Wire quality,and of sufficient guage for loads and charging source, and termiations are far more important than cosmetics. 

Its hard enough to make wiring look organized without worrying if +&- are equal length.

Now, if one were parallelling multiple batteries through a buss bar. Id want equal lenghth on all runs between each battery and buss, so all batteries shared load and charging sources equally. Or as equal as possible. But if all reds were 18 inches and all blacks were 20, id not worry.