Japan is like Europe, including France, that you should know well.
There are many Medieval chateaux in France that have never been touched, I played in several myself in my teens years. However they were mostly in ruins, no roofs, whole wings missing, staircases missing steps etc. so it was/is very difficult to visualize as they once looked like.
Chateau de Durfort as it is after centuries of neglect:
http://fr.wikipedia.org/wiki/Chateau_de_Durfort#mediaviewer/Fichier:Ch...Chateau de Ventadour in ruins
http://www.tourisme-limousin.net/photos/155/CHATEAU_DE_VENTADOUR_1.jpgChateau du Val..restored
http://www.willgoto.com/images/Size3/FR_Auvergne_Chateau_de_Val_6c08f1...Then there are all the chateaux---and also churches and private houses of various ages that have been restored, often several times.
In the 19th century the famous architect Violet-le-Duc restored many famous monument in France not as they were originally but as he thought they should be...
Notre-Dame church in Paris, the Pierrefonds castle and the Cite de Carcassonne being example of his work.
From the 1960s on restoration has been done much more carefully, by trying to restore something as it really was. But then it is not always possible nor desirable.
Many castles were inhabited continuously for centuries, in some case nearly a 1000 years. and were "modernized" by successive owners, so it wouldn't make sense to try to go back to the original building.
In famous historical castles like Versailles and Fontainebleau it has been decided that some rooms would look as when this king used them, others as that king lived
there, others as this emperor used them etc.
Even churches saw many changes and not one historical period is more important that another..
Same thing with Japanese temple..IF stonework doesn't last forever, then neither does wood...There are also all the buildings in Japan and in Europe that were badly damaged during wartime (not just WWII).
Izquierda, you seem to be a very naive person...