I'm using an EM-1 to record interviews, and twice now, it's topped out at 30mins, before simply ... stopping. No warning, no alarms, no beeps ... I can't find reference to this 30min cut off anywhere (my old Canon 7D had a documented 12min cut off) - so it's been suggested the camera doesn't actually have a cut off, but it's the memory card? It's not full, battery isn't close to being dead. Could memory card speed be my limiting factor - or does the EM-1 stop at 30mins?