It's better to have lines with extra length than lines that are stretched taught at resting position, so I'd say get some just to be safe.
I just got some extended stainless steel braided lines by Skyjacker. They are about 6" longer than my stock lines were and I got them from
http://www.4wheelparts.com/ because I got a deal on them and didn't pay shipping by picking them up in-store. Other companies make them but I've only heard reviews about the Skyjackers and the ORDs (
http://offroaddesign.com/catalog/braidedbrakelines.htm).
I don't know for certain if you need them, but it's safer and will improve your braking performance. Here's a comparison picture of mine:
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