Air duct seals are designed to last anywhere from 15 to 30 years. Duct seals should last at least as long as the rest of the duct system, itself. Unfortunately, many duct seals do not end up lasting this long because homeowners fail to have the proper preventative maintenance done on them every year. Having professional maintenance by Triple Service Inc done on your air ducts every year will ensure that both they and their sealant last as long as they are supposed to.