I think 3 minutes is what most ppl use, and you can stitch them up effortless using registrator viewer to have one long file of your whole day of driving if need be.
Registrator viewer detect your video files by time/date stamp and bundle them up into uninterrupted driving sessions, so say you have been driving from 10:00 to 13:00 then paused and then drive again from 17:00 to 22:00 then registrator viewer will see that as 2 sessions and bundle all your files within those 2 sessions.
So all you would have to do to save all that driving is click the 2 bundles of recordings and then click save, and then you will have a 3 hour long recording ( 10:00 to 13:00 ) and a recording that's 5 hours long ( 17:00 to 22:00 )
You can off course just use registration viewer manual and all the files you wish to save, and then save them in what ever length that will be.
Registrator viewer even let you cut and save just parts of a recording, and "RV" handle the raw footage and output in same unaltered state.
I don't know if the blackvue cameras have any file overlap, but if they have 1000 ms overlap like many cameras have you can enter that 1 time in registrator viewer and it will then allays remove that 1 second overlap on files.
There is demo videos of the registrator viewer software on youtube.