There is no way to make PVC that wont get brittle with age. Add in accelerated oxidation from being exposed to the elements and it will get brittle. You can slow it down with formulations or covering it but its still going to get brittle.
The church down the road was sided 1988, white in color. It looked good up until 2 years ago and then holes started appearing everywhere. You could easily push through it with your finger especially on the east and south sides. Pieces in the store room kept for repairs were still in good shape.
As far as the lifetime warrantee, most have a clause that it is only good for the original owner, and the average time spent in a dwelling in the USA is only 7 years. They know very few will stay in their house 30 years and even fewer will be able to find the documentation.
My siding is
not PVC for one thing, it's a polymer. My warranty is 100% lifetime and
is transferrable, but the subsequent owner gets prorated coverage. That's not a surprise for
any type of warranty.
Churches are so widely known for always buying the most expsenive stuff.

Sounds like they went rock bottom with 80's tech low grade siding. I wouldn't have expected any type of longevity.
IDK where that 7 year figure came from. Everyone on my street has been here at least 15 years, many for their entire adult life and are 60 or older. Most of the members of our lake club moved back to the community into their own house after college and have been there ever since. Some are in their grandparent's or parent's house. I'd estimate the majority of residents in my town have are way beyond the 7 year mark, probably by about double. Most of the vacancies we have are from people aging out to a retirement home or dying. There's not a lot of turnover at all.
Any siding companies that rely on people moving before the warranty runs out sound like the type of sleazeball cheepo contractors I would be able to sniff out immediately and wouldn't get a wooden nickel from me anyway.
Tommy