When videotapes were introduced in the 1970's, it was thought the life expectancy of videotapes would be 30 to 40 years. More recently, it has been discovered the life expectancy is less than half that, perhaps as little as ten years. Factors, such as temperature storage of the tapes, quality of tape and exercising the tape, influence the life expectancy of the tape.
Videotapes have a polyester base that has a polyurethane coating.
The coating acts like a binder that traps the magnetic particles that carry encoded information on the tape. For further information, visit these web sites.