keeping good time with excellent power reserve and accuracy for even 20 years (!) on our program. Winders are for a moon phase-perpetual calendar-tide schedule pieces that have finicky setting characteristics that you want to wear semi-often. Having said that, in the back of my mind I do think I should send in my UN Marine Perpetual ltd... but nothing about how it runs says to me "I need to be (or should be) serviced.