Something I think about a lot is the differences between automail in 03 and brotherhood
In brotherhood, Winry and Granny happily attach both Ed's arm and leg at the same time and seemingly in no time at all he's ready to spar with Al
In 03 it's entirely different. One limb is attached at once and Ed needs "at least an hour of rest" before they can attach a second one. The pain is shown as far more severe and at least on one occasion the pain essentially knocks him out and he falls asleep
I don't think it has anything to do with pain tolerance. I think brotherhood toned down the implications of having automail actually being connected to your nerves












