But we don't know how long they start dissipating. We never get a concrete statement, feat, or even an implication.
Actually there is counter evidence as well. It's stated that witnesses did actually see the light formations, even the less dense4ones created by the much slower Flashy + PS + Garou combination.
Even regular fodder humans saw them.
It's literally visible in the background during Saitamas entire conversation with Genos as well
So we definitely can't say the light lines will disappear after 0.1 seconds, they're clearly visible for a long time