When your request is accepted, RG notifies you, and the full text of the requested article becomes available for access. If no action is taken on the other side, you'll still see the 'Request Full-Text' button 'toggled'. When it is declined, apart from not providing the full text, I don't know how RG handles that -I assume RG doesn't notify, leaving things as is. The timing of acceptance/rejection is all on the author whom the paper was uploaded by.