The back staircase, from basement to 3rd floor, has been replaced at least once in the last 50 years. That is a relatively easy project, as the stairs are not "integrated" into the surrounding structure.
The front staircase, in the front room, is another matter. It is still in its original condition. The treads have worn/broken to a point where they might become a saftey issue in the near future. Replacing them will not be as easy as the back stairs, as the treads are integrated into the surrounding woodwork. We are also going to need to match the replacement treads with the existing woodwork to preserve their historic nature. They will also need to be replaced in a manner that does not damage the the surrounding woodwork.
Other than the treads of the stairs, the rest of the woodwork is in good condition.