The failure mode is ALWAYS the cracking of the plastic intake pipe on the top corner due to thermal fatigue and outmigration of plasticizers which causes the plastic to embrittle.

I'll agree that that's the most common failure. The hot coolant entering causes the inlet tube and that end tank to embrittle faster than the cold side (due to the slow loss of the plasticizers), however the new Blackstones have an Aluminum sleve insert mounted in the inlet tube to help strengthen the tube against cracking. It doesn't eliminate the problem, but it helps the intlet tube retain some strength when the radiator gets old. -it does not prevent the tube from breaking completely off, which I've seen on two cars before.

No way anybody can get 15-20 years out of these units and sleep at night.

I probably should have clarified my statement with my location, Michigan, and since it's a cooler climate than South-CAL or Nevada, my radiator will probably have a longer service life than the ones in those climates. Here in Michigan, 12-15 years is a typical life for a Blackstone in a Turbo equipped Volvo. The non-Turbos are usually good for 15+ at least due to the cooler operating temps, unless the radiator receives some phsical abuse like resting a battery on the inlet tube during installation. FYI, both my '87 240 and my '88 780 still have their original radiators, and they're still looking strong and healthy. I do plan to swap the 240 radiator at the next timing belt change with an almost brank new one that I have on the shelf. I'll still keep the old one around, since one of my friends or someone in my area typically needs one from time to time.

Here are some other Blackstone failures that I've seen:
1. Automatic tranny cooler leakage, causing a pink milkshake in the transmission and killing the clutches.
2. Nipple to cooling system resivouir bottle broke off. Didn't seem to have been mishandled or abused, but the radiator was 17 years old (non-Turbo).
3. Cold side end tank separated from the aluminum core center section. I traced this back to a stuck cooling system pressure cap that had locked closed. Both the heater core and the radiator started leaking coolant just after the cap was replaced.

God bless and I hope your Blackstones live long lives.
Fitz Fitzgerald.