Paper has the longest history of longevity, with documents dating back for centuries. For the family historian, they need to be aware of the numerous devices available to keep their precious research safe and how long they might expect them to last. Typically, it has always been the paper pedigree family charts, along with information and notes written or typed on paper that has been kept and handed down through the generations. The last 15 years has seen an explosion of other methods to keep copies of one's family history.
By putting the information in a computer software program it can be organized very nicely. All that digital data is on the computer's hard drive. Some experts estimate that a hard drive will last for 1.5 million hours. Yet, in reality, most hard drives have a failure rate within 8 or less years.
So the researcher needs to storage the information on a back-up system. If they use a computer disk, either a CD or DVD, it is estimated the disc will retain all the data for 2 to 5 years. There is the possibility of even 20 years if higher quality disks are used and the disks are stored in a good climate controlled environment in an upright position. If the disks are not cared for they would become unreadable.
Besides the digital data, there are family photos. The acetate based film might only last a few decades. Whereas the newer polyester-based film has the possibility of lasting 500 years. Photos of ancestors dating back 80 to 160 years have already stood the test of time. To ensure their survival, they must be kept in acid-free sleeves, out of the heat (no storage in hot garages, attics or basements) and low-humidity. As a back-up scanning the photos to digital format will ensure the images of great grandfather and other ancestors will be available in the future if something did happen to the original photos.
The family historian may also have cassette tape recordings or video tapes (VHS) movies. Generally, they last just a few decades, again, with proper care. As a back-up, those tapes can be made digital and placed as a back-up on a disk.
For paper documents; family marriage records, birth certificates, baptismal records, military service records, diaries, journals, letters, etc. have those scanned so they can be kept in another format. Preserve the original documents using acid-free sleeves, in low-humidity and climate controlled.
With the large variety of storage methods, as many as possible should be used. When newer and improved devices become available, transfer the data. It is extra work, but worth the effort to help ensure the survival of one's family history.