Incubation: I'm hand turning. Would it be best to turn 3x a day instead of 5x since I'll have to be opening the incubator each time?

My egg turner only fits 12 eggs and I have 18. So I'll be hand turning. I'm guessing they won't all be fertile as that happens sometimes, so I'll throw away the ones that aren't and maaaaybe I could get down to 12? But hopefully not. Since I'll be opening it each time I imagine that'll mess up the temp/humidity a good bit. Would doing it 3x a day instead of 5 be best? Anyone had any luck this way?