I shoot long ceremonies and interviews and the reliable setup has been a full size SD with a V30 and U3 mark. That keeps up with 4K 30 and the common 4K 60 profiles on mid tier bodies. For the rare high bitrate all I mode I swap to V60.
A few practical things that help avoid buffering. Format the card in the camera before important sessions. Do not run cards to 100 percent full because performance can dip near the end. Keep the slot door closed and the camera cool when possible since heat can slow cards. Do this and you should get hour long takes without stops. No drama.
