Okay, but only because I owe you...
50% was to keep the air cells from growing. Mission accomplished. However, for lockdown you'll need at least 60% RH to soften the membrane and make it easier for the chicks to zip. Once the chicks move into hatching position, their metabolism is going to skyrocket, and the moisture loss in the egg is going to speed up. You need to keep it high to compensate for this.
Edit: I read it too fast, and was in a hurry to get forgiven. The answer is yes... keep it at 50% until lockdown. Then crank it up. Sorry....