In Matthew 16:6-12, when Jesus said "Oh ye of little faith", he wasn't talking about the size of their faith being little. Jesus told them in another place (Matthew 17:20) that if they had the faith the size of a mustard seed (which is very little) it was powerful enough to move mountains. So He couldn't have been reproving them for having a faith that was little in size but little in duration. That it was a brief faith which didn't stand the test of time. In the context, the disciples were reasoning among themselves about not having brought enough bread with them and Jesus had to remind them of the provision of the awesome miracle of the loaves and the fishes which they had recently experienced TWICE! He was reproving them for having a faith that was little in duration, not for having a tiny faith.
