I wonder about this every time I replace a coil that is toasted. There are several types of coils now (Ni, kanthal, stainless) - it'd be nice to know more about the degradation of the metals and its effects for sure.
Kanthal requires a very specific heating profile after installation to develop its protective coating. Without that its basically just weird, fancy stainless steel. It becomes very brittle after the heat treat which causes gradual degradation especially during repeated, fast heating cycles. I would not use it.
I would also avoid low-alloy stainless like 400 series. That's the cheapest kind and at elevated temperature it oxidizes and corrodes. 300 series would be better, 500 would be best. Even within those two series though, some alloys will be much better than others.
Nickel... I don't know. It's very sensitive to composition and some can leach into liquid and others don't. It's more toxic than iron or chromium, but pretty resistant to temperature. Kind of a wash.