A family member just bought an old Boston house with K&T wiring. They wanted to do some renovation, so that meant bring it up to current code. It was quite expensive, but I told them do it, renovation or not.
Like I said, 70 year old wiring is scary, the K&T stuff, while robust for what it is, has had decades of folks potentially monkeying with it, and is not in any way to be trusted with modern household devices.
That's money well spent to fully replace the wiring in those old houses. Most of those old knob-and-tube only had a 4 or 6 circuits in the house. Completely inadequate.