I only looked up the HEddal stave churches and It stated that they were re designed at least three times with a total rebuild of one of them in the 1950's. Im sure the others underwent similar roof rebuilding. ITS virtually impossible for such structures to withstand almost 1000 years of chemical erosion. The roofs are Shake an where do shake roofs last 1000 years? Im sure theres no miracle in the material here
The Wiki stated that there were thousands of these churches in the 13th century of which obly 29 remain today (all the others either rotted or burned or were otherwise destroyed)
Im sure the other hurches on the "extant" list were rebuilt more than once
WOOD will last indefinitely unless it gets wet. We have 300 year old barns in the county and, if a leak happens in the roof, a barn can rot away in 10 years if the beams aren't protected rom the weather.
Of the almost 970 of Norways stave churches that rotted or burned, most actually rotted because they were built in a fashion we call "pole barn" where the upright beams are driven into the ground. A pole barn has about a 50 year life , but many farmers will, after about 10 years, construct astone or concrete"Sill Plate" where the uprights (the staves) are resting in a masonry foundation and not on or in the soil.