What is iPhone 6 Plus 128GB 1080p 30fps Maximum Video Time Length? What is iPhone 6 Plus 128GB 1080p 30fps Maximum Video Time Length?

Is it "Available Storage Space," or is there already a fixed time limit? Digital Still Cameras are generally restricted to 29 minutes because of tariff restrictions (vs. being categorized as a video camera). Will iPhone 6 Plus do the full 29 minutes, or longer, or is there a shorter technical time limit?
I believe limit is only storage space and power.

For sure there is no 30 min limit on duration since last time I did 55min video without any interruptions.

And since bitrate of the video is variable depending on the scene there is no fixed time limit per GB either.