#10 will just eventually die a slow death hooked up to a 40 amp range.
Well yeah, that's why the inspector made us use 30amp breakers
We always just do it now and it only adds about $500.00 to a reno if you're already there.
In a house mabey but try that in a high rise apartment building using BX. It will cost more than $500 just to patch the holes! Also the old ones are hardwired so changing to a receptacle in a wall that was built 40+ yrs ago tends to take some time.
I've seen some attics where the bare copper got exposed in some places where the cable just succumbed to the current to feed the range.
The ambient temperature up there doesn't help either, that's why we have to de-rate wires in attics [CEC 4-004(8)] Although it's rarely done