Fishin The Riffles

[Riverview]

Have been having some good luck fishing the riffles this fall. My question is how far downstream of where the riffles start is still good water to fish. I pretty much jump in right at the riffles or slightly below, some areas turn into deep water but some stay shallow for a long ways, are there still fish in these runs or are the fish generally sitting right where the riffles start.