It should stay there for as long as those lates report. IMO, ignore Experian's classifications. Sometimes they have been inaccurate for me (e.g. says an account is good but FICO sees it as bad).
Per FICO scoring, those 30-day lates damage will fade over time and within 2 years or so from that date, FICO will largely stop scoring them.
It will stay in the bad section until those lates are off. They fall off naturally 7 years from their respective dates or you can try and GW them off.
Side note. llecs is outtyping me this morning.