PCV Box, performance, and root cause of sludge?

I have a 99 Volvo s-80 2.9L non-turbo. I have been through a lot with the car that I won't get into but the latest is that the dealer's service people say that the car needs a new PCV box because it is sludged closed, they think. I am a little skeptical, especially when they quoted me an $800 fix including a $150 price tag for the part. I looked at the service bulletin and it said "get to it, clean it and retest... 55 steps or so." I also found the part online, at the second site I looked at costing $33.42. Unless my dealership is getting the part directly from Sweeden in a lacquered wood box on a velvet pillow, I don't see $120 in markup on the part being justified, even at the dealer. Additionally, my car is popping a code for something completely different.

So, the first question is this: In driving the car, would I notice a problem with the PCV box in the performance of the car? If so, what would that be?

The second question is: Is replacing the PCV box something that I should have expected in 95K miles of driving the car? If not, what might be causing the sludge that may or may not be there and is this something that might need addressing (likely more expensive addressing)? If so, who the Hell designs a car with something that is definitely going to go wrong that takes four hours of labor to get to and put back? I love driving the car, but hate fixing it. Next car will likely be Toyota or Honda at this rate.

What sludges up the PCV box is not changing oil often enough. The lower quality the oil is, the worse the sludging. I've seen sludged up engines with less that 30k miles. As it clogs up, it loses effectiveness in pulling the oil vapours out of the blow by gases, thus increasing oil consumption. As the box clogs further, there is not enough flow area for these gases, and pressure builds up. This will cause oil leaks, and as increased amounts of oil end up in the intake manifold, coating throttle bodies, oxygen sensors and catalytic converters.

740s and 240s have this same problem, symptoms just aren't as noticeable. Their oil traps aren't as complex, so they stay functional longer.

I would imagine the dealer's $150 includes hoses and clamps, which should all be changed at the same time and gaskets to put everything back together.

Nice how Volvo doesn't take ownership of this problem, instead hitting owners for "maintenance".