I use skinny dyneema cord for my tarps so bulk and weight isn't an issue, therefore I use a continuous ridgeline (CRL) of 10 metres or more, depending on the trip and trees. The biggest advantage of a CRL over separate cords tied to the ends of the tarp, is the flexibility of being able to slide the tarp with the prusiks to exactly where you want it, usually central over the hammock. With separate lines, to centre the tarp you have to faff about with untying and retying your knots until you get it right.