I doubt the maintenance is that much more expensive, however the Villas are larger than most houses and old, so might be in need of more repairs that a younger building! Unless you are repairing the deep skirting or similar, the plaster, paints and materials used internally are all the same.
Also, I doubt some of the "Experts" advice that the Villas were all Lime rendered, we had some removed as part of a structural repair and they had to use angle grinders to cut sections that they could then chisel off, the pieces would ring like ceramic when tapped with a metal tool. The structural engineer's said that is was definately portland cement render.
Remember Portland Cement was invented in 1824 by Joseph Aspdin, The Villas built in 1852/3. The render in question was inside the house, under the plaster in a bedroom, it was there due to alterations to the building that moved the front right side of the house about 3M forward, causing the already rendered side wall of the porch to now be inside the house!