The Browning design is very durable so it's not so much years of service as rounds fired. I have put over 30,000 through a 1917A1 and 20,000 through an M37 and the only part I have had to replace is the commercial made 8mm barrels that burn out about every 8,000 rounds. I did have to replace an extractor cover spring on my 1919A4 semi once. That all being said I do keep a set of spares on hand. Sear, Sear Spring, Firing Pin assy., Extractor assy., Recoil Spring, Extractor Cover Spring would be the basics. You will eventually end up with a complete set of parts as spares.