In your shirt pocket

Stored in a humidor which has a moistureizing capability, a good cigar should last months.

Cigars should be stored at 70 degrees F, 70% humidity. The hotter it is above 70, the more you should lower the humidity; the colder it is, the more you should raise the humidity. If you're looking for something cheap, small, and simple, that will keep your cigars for weeks and even months (but not years), the best poor man's humidor is a simple if largish piece of tupper-ware. To humidify your cigars this way, take a new regular small clean kitchen sponge that hasn't been chemically treated, soak it in distilled water, squeeze out all the water you can, and then place it in a smaller, lidless piece of tupperware in a corner of the large one, and don't let the cigars touch the sponge, and don't stack them over it. Keep the big tupperware sealed, and check every day or two for (a) mold and (b) to see if the sponge has dried out and needs to be re-watered. Remove any moldy cigars immediately, and you should probably at least quarrantine the ones touching them in a separate container. If you catch it early, the cigars are still okay to smoke. If you are looking for something more high end and long term, you'll need a VERY large humidor, preferably a walk-in one. But lovely wood desk humidors are only good for keeping the cigars you'll be smoking soon, and are almost impossible to keep at the right humidity level. Cigars should be kept in their box until you're ready to start smoking them, though you may open the box and-if wrapped-an end of the wrapper. If not kept in a full box, they should also occassionally be turned, just like a bottle of wine, but for different reasons. Cigars of one type should be stored together, and should be separated from cigars of different types -- they can be in the same humidor, just not the same box - at least not for a long time (a few days is okay); different types should be separated from each other by a good bit of air space and/or cedar dividers. If the cigar comes wrapped in plastic, open an end, but don't remove it: it will help to keep it from absorbing or communicating flavors/aromas from or to other types of cigars in the same humidor. Be sure to check your humidity and temperature regularly, and check your de-boxed cigars for mold. Kept properly, a good cigar will last for years, even decades, and will improve as it ages. If you have some nice mild (or even bland) cigars, you can greatly improve their quality by aging them over cognac or some other liquor you feel will enhance and complement the cigar. You just put a shot glass of the stuff in the humidor, preferably on the bottom shelf/in the lowest drawer beneath your cigars. Keep checking for mold and dryness as usual, replenishing the liquor as needed.