I would say if it's longer than a week from your initial trade you should be fine. Usually the only bans I have heard of are trading over weekend, ban happen early the week after when jagex are back at work
I imagine they would take action as soon as they are aware so they can get the gold out the game also
This is different to what happens with botting, as they do delay bans to monitor the behaviour of the bots and also so boys aren't always aware of what action got them banned