Here is info showing how long you can record at the different Hero video quality settings ...
https://havecamerawilltravel.com/pho...ze-gopro-hero4
I don't think you get very good quality at 6 hrs ... Way too much data at the higher quality video settings ...
I think you'll want to find a deal on multiple cards and manage your recording in smaller increments of time - but with higher quality ...
Rickie