I'm averaging under 5 minutes from ticketing check-in to clearing security since March (when they seem to have improved things). But it really does vary a lot by terminal and time of day, it can take 2 hours at Southwest (which is always the worst for delays at LAX). Overall LAX is no worse than any other airport in the US, despite its fearsome reputation, and often better. The worst delays are at 6 am and midnight, times that might surprise you but logical given the flight schedules.