I'm not using pre-packaged tins, but bulk bins from the LHB. If you saw the way they dispense LME <shudder>, you'd boil it too. I understand pasteurization typically occurs at 180F, but I prefer to be safe. And I don't stop the boil to add the LME - I stop the timer until the kettle is back...
Not to drag up an old thread, but I've recently started late additions of LME and have been doing some reading. The method I came up with is: 15 minutes before the end of the boil, dump the LME and 1L of boiling water into a pot on the kitchen stove. After stirring to get a consistent liquid...