The sights themselve are made of metal. The fiber optics would last indefinately unless broken, at which point you could probably just replace the rods. The Tritium is a differant critter. I have tritium sights on another of my guns and they are 5 years old and still work just fine. Maybe someone else knows of expected life of tritium sights, (Sounds like a google search)
The cost at Shooters for the Sights was $99.95 Installed.
And I can move them to another Sig if I wish to.
Chief