Ammo Boxes
Ammo cans can be a great way to keep your ammo organized, stacked, and dry. However, ammo cans are not the only way to do so. Tupperware-type containers, plastic food-storage buckets, and gallon zip-top bags can be excellent and inexpensive ways to keep your ammunition sealed away from moisture.
Ammunition isn't a perishable good - if stored correctly, it can last almost indefinitely. Whether it was stored correctly or not is another matter. Ammunition isn't like the still-edible 5000-year-old honey found in Egyptian tombs; ready to eat and spread on toast.
Generally, yes. If factory centerfire cartridges are stored in a dry, cool place with low humidity, preferably in an airtight container, they can have an amazingly long shelf life. Many ballistics experts who have shot tens of thousands of rounds over the years report shooting 20- to 50-year-old ammo with no problems.