Unfortunately, the physical makeup of more modern paper products means that eventually they will disintegrate. Acidity of the paper is the primary reason most documents will not last. Paper is acidic because it is made from acidic pine trees soaked in sulfuric acid to pulp them (that causes the characteristic smell of a paper mill). The pulp is bleached, which cuts down on the acids but adds a corrosive alkaline. When exposed to heat and humidity, these acids and alkalines oxidize the tiny strands of pulp that make paper. Paper is also physically weak. It has a grain that accepts folds easily. When paper is folded over and over again, it tears. The act of unfolding and refolding shortens the life of the document.
Printed photographs also have their own inherent vices. Prints and negatives have light-sensitive emulsions bonded to a backing that can separate. This is particularly problematic with old tin-type photographs. The bonding agent is just not strong, and the picture flakes away. The emulsion on all photographs dries slower than the backing, leading to curling, rolling, and cracking of the image itself. Photographs are also subject to scratching by dust, dirt, or rough storage envelopes, and scratches can happen before you know it.
How archivists file and box papers and photos is important, and genealogists should learn from their techniques.
When it comes to choosing boxes for storage of your paper records, use acid-free boxes if you can afford them. If not, tightly pack your boxes and file folders to reduce acid off-gassing. (Not having an acid-free storage plan will increase acid transfer from direct contact with file folders in your boxes, however, so to slow this process down, insert a blank sheet of acid-free paper everywhere a folder touches valuable documents.) Tightly packed boxes and file folders also provide physical support for the records, which prevents bending, flattens crumples, and makes them easier to access and handle. Never use hanging file folders, however. They cannot be packed together tightly enough, and the documents have a tendency to become damaged in the hanging files. Pack your paper records tightly into file folders, then into (hopefully acid-free) boxes you buy at the office supply store, and put them in your chosen safe location.
When it comes to photographs, you can put them into plastic bags, even sandwich bags, to keep them from sticking together. Ideally, you would want to place them in acid-free photo envelopes. You must not place tintype photos in plastic bags, however. Store tintypes in acid-free protective covering. When labeling your photographs, only write along the back edge in pencil. Better yet, identify the photo on a piece of paper, and stow that with it in its bag. Pack them moderately tightly in an acid-free photograph box, too.
Once you have everything organized and into safe storage boxes, you are ready to find a place to store your collection. In general, there are a few rules to keep in mind for storing and preserving records long term. The first has to do with the environment you choose for storing your items. A good rule of thumb: if you would not want to live in a place, do not make your records live there. The storage environment should be free from dirt, chemical off-gassing, bugs, rodents, and water leakage. Do not store records in an outbuilding or attic where temperature and humidity are not controlled. (In an ideal world, you would store records in a location under 68 degrees and around 45 percent humidity, but if that is not possible, then keep them in a temperature-controlled place.) Also make sure the records are kept in dark conditions (light fades paper); a good place is in an acid-free box in a closet or under the bed.
With a bit of knowledge and some gumption, storing records for a reasonable time (before donating them to an archive, of course) is a pretty simple task after all. Do your descendants a favor and preserve their history in the best way possible.