I'll check out the the Time Out option. I've been having pretty bad performance issues with recent versions of ArcGIS on my systems, so that may be making the problem even worse. I ended up having to run the unmatched addresses through the rematch process 4 or 5 times before it stopped finding new matches. Wasn't a lot in the end (about 60 matches out of 20k+ addresses), but it is disturbing that the same address might have different results depending on when you run it.
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