I use a sealed container and usually don't open it until it's time to cut. On clutches I am really looking forward to I do sometimes open it at about day 40 to candle the eggs and see what I got though.
I didn't vote, because I use the same method as John. Never had any problems with not ventilating. The eggs don't have a very high oxygen demand. The babies get oxygen via the blood vessel network in the egg.