I had a (small) fire in the wall of a house in about 2000. Turned out the rubber insulation had fallen off the wiring, in various places there were just pairs of bare copper wires. An electrician friend helped me rewire, and we layed in cat5 and conduit (between storeys) at the same time. Rewiring a house from the 1840s required pulling up floorboards, but no significant work in the walls.
I'm not sure whether older houses are more maintainable by default, or just once you have rocked over some threshold of continuous occupancy, there there are sufficient layers of repair and rework that you just stop worrying about (for example) sawing through a floorboard. While I didn't have to mess with the walls, if I had, I'd just have torn down the existing plaster and redone it, like you say it's not that big of a deal
I'm not sure whether older houses are more maintainable by default, or just once you have rocked over some threshold of continuous occupancy, there there are sufficient layers of repair and rework that you just stop worrying about (for example) sawing through a floorboard. While I didn't have to mess with the walls, if I had, I'd just have torn down the existing plaster and redone it, like you say it's not that big of a deal