Yep, there's a lot of bad, or at least 50 years outdated, information that has been perpetuated in homebrew books and such. On specifics, let's see. Boiling decoctions doesn't cause astringency problems, so 170°F won't either. DMS is not even a problem except with the occasional extra pale Pilsner malt, and even those are manufactured to minimize SMM (the precursor.) It takes at least 30 minutes on heat to convert SMM, if it is even there, to DMS. Then just a short uncovered boil will drive it off. A gentle, circulating simmer with the lid on is far less damaging to wort. And so on. Like Jim's point on not sweating the trub removal. Lots of stuff had validity once, but either materials have changed, or brewing science has advanced and debunked old assumptions and practices. There are great resources to stay on top of things at least, like the forum for one! There are also podcasts, websites, professional textbooks (newer ones at least)... But this forum is always eye opening and a good start. Like right now.