Ah see, I interpretted 'day' in the literal sense there, not in the 2 QD=a Work Day.
But, assuming you are correct, wouldn't that mean that in the summer you never have a roll at night, since you only spend a QD asleep?
Personally, I would maybe change the rate that you roll based on how hazardous you as GM determine the hex to be. Maybe not RAW, but if you are in a hex close to a 'safe' populated area I would roll less than if you were in the middle of the wilderness near to a dungeon/monster lair etc.
I think there should be some amount of "it's up to you" when you want to roll for random encounters rather than sticking to the RAW for that. If you think your adventurers are having too easy a time dealing with things, then throw in a couple of unexpected encounters when they are camping just to keep them on their toes.