If he doesn't have any flashes or nightmares about things just on the edge of memory or anything like that, then probably there's no echoes. Like Katie knew a kid who'd been molested by the local fae baron, but he'd wiped her memories of the event. She still had nightmares she couldn't quite remember and felt creeped out sometimes, so she started forming an echo of the Baron anyway.

They still have to be kind of there on a subconscious level for him. If they've been so neatly packed away they have no impact on him at all even in minor ways, he's probably echo free.