Sooner or later every pipe organ will need to be restored. Although their musical qualities are always foremost, pipe organs are complex machines built from wood, felt, metal, and leather. All of these materials wear and deteriorate with time, and especially leather. Regular maintenance can help to slow this process, but eventually there comes a point where all the leather must be replaced. Depending on how the leather was originally prepared and environmental conditions such as temperature, humidity and soot, organ leather may last anywhere from 25 to 50 years or sometimes even longer.