Kaylia: spend it now if you play actively, and farm 4000 before the patch/cata hits and you're fine. I converted my 18000 to all the gear I can buy (mainly tank gear) and then converted it to "cash" via gems. Unless you're too lazy to farm or busy, then don't spend it. Worked out better as it was roughly 2JP for 1 gold, but I was buying gems with 110 JP and selling them for 100 gold, doubling my profit somewhat.
They'll cap you at 4000 when cata comes out anyway.
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