Graham,
Stepan does have one child...cannot remember if male or female but the child is young. I do not worry about servicing the watch for Stepan is much younger than I am and there is only one complication designed and manufactured by him on the Soprod movement. In other words, just as I have both of my grandfathers' pocket watches (Hamilton and Waltham), I had both not only serviced but overhauled within the last 2 years and there are quite a few expert watchmakers in the U.S who can handle it just as I think there will be with Soprod 100 years from now.
I am very pleased with my bespoke watch and Stepan was a pleasure to work with. I look forward to seeing many of his creations in the future.
Laurens