When you say dry box, are you talking about a humidor without humidification, of simply leaving them out on the counter. A dry box to my understanding, being a humidor (tupperdor) without any added humidification is a good way to slowly lower the humidity of a cigar that smokes better at a lower humidity that you store them at. As for how long, I don't dry box, and haven't experimented with it, so I can't help you there.
If you are simply leaving them out, that will cause uneven drying or saturating depending on your climate.
I have heard Mark, "N2adventure", speak of dry boxing. He may be able to help you with specifics.