Example of duration of Timeline content and burn to time?
As you know, the export time with dependant upon the computer as well as the nature of the TImeline that you are burning to Blu-ray disc format on Blu-ray disc.
In the burn to Blu-ray dialog, what does the Quality area of that dialog show for Space Required and Bitrate?
What is on that Timeline in the way of video (formats and duration), photos (format, how many and pixel dimensions) effects, transition, titles? What is the duration of the Timeline content?
What is the speed rating of your Blu-ray burner and Blu-ray disc (BD-R or BD-RE, 25 or 50 GB)? Internal or external Blu-ray burner?
What do your computer resources look like, installed available RAM and free hard drive space as well as processor description? Is your computer optimized including clean up/clear out of pile ups of preview files, conformed video, and conformed audio?
Is this export time matter restricted to this one project with this specific Timeline?
Let us start here and then decide on our troubleshooting strategy.