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You are the iio (userid). You should know it better.
Still, EAC # gives you a fair clue of when should one expect I-485 approval.
For example, Currently they are processing EAC # from EAC 00 007 XXXXX to EAC 00 084 XXXXX, then you know they can make a useless (waste of time) anticipation of your I-485 approval. But, i feel its the same as anticipating through others ND/RD dates.