The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
PS-The comment about ludens/lineatus simply reflects the fact that I am never entirely sure that I have the latest taxonomic info available, and that there seems to have been some debate about whether they truly deserve the species distinction. I'll certainly trust Mayfly Central on such matters. (As I do you.)
The species of interest to flyfishers, which are found in the North Carolina, would come reasonably close to your body description of deep brownish and wing description of smoky dark gray, and have a dun length range encompassing the length you describe, would be the following:
Leptophlebia cupida (Black Quill) - emerges mid-Apr to late-Aug
Drunella walkeri (Slate Drake) - emerges mid-Jul to mid-Sep
So, I would guess you are encountering Black Quills in March, and (somewhat-delayed-emerging) Slate Drakes in October.
So, I would guess you are encountering Black Quills in March, and (somewhat-delayed-emerging) Drunella walkeri (Large Blue-Winged Olives) in October.