On Windows 8, when you burn files that are large in size (e.g. > 1 GB) to a Blu-Ray or DVD disc, the estimated time reported by Windows may not be accurate.
The estimated time is not calculated correctly when large chucks of data are being written to the Blu-Ray/DVD disc. This causes the amount of time it actually takes to burn the disc to be longer than expected.
Note: the amount of time also depends on the disc writer's specification.