The conversion speed depends on not only the size and length of the source video, but also on the export settings. Your computer’s performance is also a factor. Here's a tip for exporting faster:
Export with Original Settings
If you keep the Resolution, Frame Rate, and Bitrate the same as those in your original video then exporting will be faster than if you change them. To see the original parameters of your footage right click on it in your Project media and choose properties.