too much water can potentially drown the eggs and/or can promote mold and fungal growth
i open the incubator about once a week.. i incubate my eggs in vermiculite inside punched deli cups.. the vermiculite is wet enough to hold its shape.. i check once a wekk periodiaclly on the eggs, more frequent when hatchin is iminment. if the vermiculite seems dry i will remove the eggs off to the side..and make the vermiculite moist again.. i do not pay close attention as to what the humidity is.. this method has worked for thre past 5 years. i would leave the plugs in..