My house, built in 1944, still has some knob-and-tube wiring in places that are hard to reach, although I’ve replaced most of it. As you say, it’s okay if left alone. The problem is the deterioration of the insulation over time. I went to replace a halogen ceiling fixture in the kitchen a few years ago, and found that the heat of the fixture had cooked the insulation to the point that I could crumble it with my fingers. That led to a major rewiring job in the attic to replace a couple of circuits that went all over the house.
The main problem with knob-and-tube now is that many insurance companies won’t insure a house that has it.
I’m surprised to hear that. After some bad experiences in the 1970s contractors in Ontario, and probably all of Canada, dropped the use of aluminum completely, although the big box stores still stock switches and outlets suitable for aluminum.
