I think you can file this one in the same place that you file "7-yr Maintenance-Free Batteries" - a good idea, but just not realistic. Change the fluid every now and then. As others have said, the thermostat will break eventually, and this is a good opportunity.

Gerald C

James is correct. Change the t-stat every 70K miles and if you think it looks dirty IF that bothers you but otherwise there's no good reason to ever change it as no real corrosion or coolant break-down occurs.
Now, the book also says "no trans fluid change" as well and most people, including those who work within Volvo suggest occasional fluid flushes.

I just changed mine anyway because it seems unnatural to leave the same fluid in there forever. Consider using distilled water for your mix.

If you do a search on this topic, you might find;

All the metals in the cooling system are the same or similar enough to aviod corrosion.

The environmental rating of an automobile is affected by the quantity of waste fluids that it generates during its lifetime, hence no periodic antifreeze or transmission fluid changes are reccomended.

Change the antifreeze when cooling system work is done. (That is what I did.)

And so forth.

Somewhat curious.
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3 8s & 2 7s 725,000 miles total