Under ideal conditions mine are good for 2-3 weeks. Ideal conditions are cool (45-55F), even temperature with as little fluctuation as possible and never any direct sunlight. My truffles also will pick up smells if there is any strong scented things in the area. If it accidently gets too warm or cold it can do all kinds of bad thing to the chocolate- condensation, melting, bloom and none of that is good. I don't have a humidity issue to deal with. That might be another concern of yours, depending on where you live. I have also noticed that the better I get the temper on my chocolate, and when they come out shiny and hard they keep the best also. Good luck.
P.S. I have kept truffles for 6-8 weeks in good conditions and they don't necessarily go bad, its more of them tasting stale. A friend of mine put some in the freezer and swore they were good for a couple of months- but nothing I would sell.