A: On average the pack you get in your cigar box from the retailer will last about a month. The Boveda packs you get when you by them individually or by the box are noticeably thicker and have about 3X more solution in them. They will last up to 90 days. The way to tell they’re spent is to feel them. When the packet starts to feel a little crunchy, the crystals are beginning to dry-up. The packet will feel stiff after the crystals have exhausted all of their moisture.
By day 30, if the cigars have some good spring in them when you pinch them, they should survive long enough for you to finish the box. Just to be safe, you might want to pick up a couple of Boveda 69% humidity packs (shown), for back-up.
Finally, one method you can try when using the humidity packs in a factory box, is to place the pack between the two rows of cigars. This ensures that the bottom row will also get their fair share of humidity.