I think they've been in town for awhile(Iris and John), Iris shares a dorm with Alexis for some time now (one semester maybe?), Iris and the MC split up before the flashback that introduces Cara/Nikki(his stay in Riverside isn't clearly defined but feels like at least 2 months to me), and apparently he had the time to nail a whole bunch of girls before moving to Riverside.that's what I thought too when i first read his theory about John but then i figured maybe he was back longer than we thought like 2-3 months or something and we just never ran into him to know.