One thing not mentioned is that the continued practice of shooting 38 cases in 357 chambers can leave a nasty soot ring built up just in front of the case mouths.
As most of us are pretty dilligent about leaning our guns, this will likely never be a real problem.
I only bring it up because the model 66 I bought used last month had this condition to the point where it wouldn't chamber factory 357 ammo without signifigant force. I don't know how much pressures might have spiked, because as soon as I discovered this problem, I unloaded the gun and cleaned the bejeebers out of the cylinder.
I am guilty of loading HOT loads in 38 cases for use in a rossi 357 levergun I had. It was built like a safe, and I assembled some pretty insane loads for it before I became older and wiser.