I think that the ally conducts heat away so fast that it can soak up a far bit of heat ,and I think you gain more by heating moderately and cooling a few times than you do by over heating it onceI use map gas and go forever....sometimes the original OMC paint doesn't even show much harm amazing stuff.
Acetylene, map gas I've used them all. Map gas or an induction here is all you need that in a few crayons.