Guess I'm fortunate
in 1930s and in this part of Ca, Redwood was common for building. Most of the floors are Oak. I'm also fortunate in that both my house, and the house next door were built by local lumber Barron's. They did all of the milling for the homes built here in town during the late teens through the 50s.
House has all of its original doors and windows. Including the hardware, and skeleton keys.
Through the years I've done my best to keep things repaired and maintained. Just fixed the first and only window that the rope holding the sash weight broke.
House still has the knob and tube wiring, (has never failed) original furnace, and original phone, and wires! (not to the pole) original cast iron plumbing is still working with no leaks ..with the exception of the laundry sink, (plumber was a idiot and cracked the old cement sink) so that's relatively new.
A ounce of prevention can go a long way to keep these old house in good working order.
Maintaining roof, gutters, down spouts, repairing cracks, to keep water out, re painting wood windows, replacing glaze, oiling sides dose a lot to keep them solid and operational.
There's one bad spot that water was getting through and I didn't know it...leak is fixed but hope I wasn't too late.. We'l see