In my AU, Surge is the "definitive cyborg", which means that the same metal virus inside her body will continue to fix her cybernetic parts. The only way to stop this is to disable a very little part of her skeleton, which only Starline knew where it is placed. Still, in post LTMEA, when Surge gets better at trusting people, she still gets checked out by Tails, just to be safe.
Autumn and Kit are another story, which the first is a very rough prototype cyborg and will decay very soon and Kit has got his weakness spot, found in the core of his backpack, destroyed by Starline before the platypus would die. This caused Kit to be unable to fix himself and decay later in the story as well.