So long as you can keep your Z2 cool and have enough space, 4K recording has no limits! I was out to see fireworks on the 31st of December and I usually got around 2-5 minutes of 4k recording before overheating starts but that was not the case that day. It was cold and I decided to get the fireworks on display in 4k! surprisingly, it just kept on recording and never stopped or showed any warning message. I ended at exactly 30.00 minutes cause I had no gloves on and my hands were going num LOL. I think it's safe to say that the temperature of the surrounding affects this feature as in normal circumstances, the sanpdragon 801 inside the Z2 produces too much heat when it's put under high workload. Maybe in the near future with better SOCs like the Snapdragon 810 and so on, manufacturers will do a better job with heat management.
