I finally removed the last of my K&T wiring last last month in my 104
yr/old house. The wiring was the first generation installed in the
house (sometime in first half of 20th century). My house had gas lamps
originally.

The K&T was in relatively good condition. The insulation on the wiring
was a little brittle but still fairly strong. My biggest concern was
where new wiring was connected in. I often found connections without
J-boxes and covered by insulation.

-borninPA