As we already know, the best place to store your cigars is in a properly maintained humidor. However, there are some cigar humidors, like cabinet style humidors, et. al. that are big enough to accommodate entire boxes of cigars. One of the most often asked questions about this type of storage is whether the humidity from the humidor will reach the cigars in their factory boxes.
If the conditions are right, cigars that are kept in their factory boxes will stay fresh up to a month on average, even after opening. By placing the entire box in your humidor the cigars will remain fresh indefinitely, just as they would if you removed the cigars, but it depends on how you plan to store the boxes, too. For the purposes of this article, we'll assume you are storing your cigars for the long haul and that your humidor keeps pretty stable "ideal" conditions.
By keeping the boxes sealed with their outer cello on them, this is not much different from how they are stored in a humidified warehouse or a cigar store humidor; the cigars should be fine. However, it's better to remove the outer cello from the box, which will allow more humidified air to seep into the box. Moreover, cracking the lid - in other words, lifting it an inch or so - will allow even more humidified air in, and it is recommended that you do this every so often. You can use any number of small objects to prop the lid open. Anything from an extra cigar cutter to a cedar spacer block, even a rolled up business card will do. You can keep the lid propped up for as long as you deem necessary. 24 hours is usually plenty of time.
Of course, removing the lid entirely permits the most air flow, and this practice is also quite popular with many cigar smokers who have cabinet type humidors.
Finally, cardboard boxes are packed tighter than wooden "cabinet" style boxes in which the cigars themselves are also not protected by cello. Wooden boxes are also preferred because they're made from Spanish cedar, thereby augmenting the positive effect Spanish cedar has on aging cigars.