When we moved in the house had a combination of Romex(sp?) BX both copper and aluminum and whenever they needed another plug or switch they would "hide" a junction box to make the connection somewhere where it was impossible to get at. Some weren't even screwed/nailed down to a floor joist and just left hanging.
The wires were all resting on the edges of the boxes waiting to cause a fire.
Needless to say we ripped out all the wiring, put in a sub panel with a heavy duty 220 line from the Garage (main panel) and then rewired the basement and anything upstairs we could gain access to from the basement into the new sub panel.
So the whole basement is newly wired with copper and the whole upstairs is still original Aluminum. Unfortunately we would have to break walls to replace so we left it as is. We did replace the Stove/fridge wiring with copper because these are higher drain devices that weaken aluminum over time.
My dad calls them shoe-makers, I call them drunk-monkeys!