The life span is probably more due to the lifespan of the plumbing. On high-grade copper(L- or K-) you can get a useful life of 50 years but PEX is only rated f

The life span is probably more due to the lifespan of the plumbing. On high-grade copper(L- or K-) you can get a useful life of 50 years but PEX is only rated for 30 years, and the lowest grade of copper(M-type) has a similar replacement interval. The valves used in plumbing fixtures also wear out and need replacement periodically. And the valve housings do as well. The anode in a water heater will probably only last a couple of decades. These are all replaceable parts. Siding is in a similar state, with many modern sidings have replacement intervals in the decades, and shorter time periods if you don't paint every 5-10 years. If properly maintained and if parts are replaced in a timely manner a house can last indefintely. My partner and I own a house from 1935 that was last renovated in the 1990s, and I'm starting to have to make minor plumbing repairs. I think in the next 10 years or so we'll have to re-pipe and re-wire. But the framing and sheathing is almost all original, except for the roof deck which was replaced first in the 1990's and then parts were replaced when we re-roofed last year(the original roofer did not know how to frame to support a rake board). Everything also changes if you factor in repainting and replacement of interior fixtures. But still, if you maintain it and factor in all these repairs and replacements your house can last for hundreds of years.