I think we need to stop fretting on the 90 second thing in the discussion. While 90 is the certification spec it has never been assumed that it can be achieved in normal operations with real passengers. The time allowed was originally 120 seconds, but in 1965 it was thought that newer slide designs would allow evacuation to be quicker and so 90 was selected. It doesn't really link to survivable cabin conditions or outcome studies. It's a bit like car fuel efficiency reports, a standardised way of assessing things but very different from real life.
That said I support a review of the standards with the changing demographic and physiology of travellers.