I have been involved with icing research and FAA rulemaking on the topic for many years, and I have to say that this question has never come up so far as I am aware. It is a very good question to inject into the discussions within the authorities. I will make some inquiries, but as has been pointed out, the exact wording of the AFM or FCOM is crucial.
In my experience with the 757, a landing with a 20 knot maximum speed additive results in a pretty shallow deck angle, with the resulting derotation being, shall we say, brief. I suspect that this limits the cumulative additive as much as anything.