I agree it is optimal to redress for each blade, but I was not taught to even by the really good techs who I trust a lot.
At the rink we were not even told to do it fresh if the last used radius was the same as what was requested. That was almost only for hockey though and recreational figure blades. Those guys always seemed really happy with my sharpenings and had me fix badly done jobs pretty often. It felt really nice when someone would come back and tell me how much better they felt on the ice after a fix.
Anyway, I am apparently not very sensitive to how well or poorly done a sharpening is, it seems, but I think the best possible effort should be put into it by a tech. It’s really not so hard to make sure every bit is done well, so I’m baffled by how frequently people get awfully botched or somewhat poorly done sharpenings.