Definitely have to say the time last year when I tried to unclog a drain myself at my 3 family home and being old cast iron it was so brittle that it snapped where it connected to the main drain.

If they are old, brittle, and worn anyway, I possibly wouldn't charge for that and just replace them. 

I dont like how CPVC can get brittle with age, so I would personally replace with PEX if you had to do repairs and can tie the repairs back to the CPVC adequately. 

Spend the money on a decent tray or they get brittle and wear out.

Wear & Tear are things like: faded or brittle blinds from sun, minor knicks on wall, loose doorknobs, carpet wear, faded paint.  

The old covering becomes brittle over the decades since it was installed and overloaded, can and often does pose a fire risk. 

It looks like someone used wood filler to fill in gaps and it didn't cure properly, now it's brittle. 

Some of that really early insulated wiring is kinda trash--the insulation gets brittle and disintegrates, which is (to put it mildly) not the best, but that's not what he's saying. 99% chance you either misunderstood or he is lying.The bathrooms have mold because they're damp.

mostly due to the auto clean spray that makes it brittle. 

That's also very useful info about the rodents--one more reason to take preventative measures.I was thinking of it from the perspective of how materials break down (especially with heat/cold cycles)--typically, rubber and plastic type materials break down faster in a car's engine bay than the metal materials, for instance...which makes me think pex would break down (become brittle) faster than copper....but, I'm no engineer, so who knows...