It should remain how it was when you started. If it's drying out alot you have to many ventilation holes. I prefer putting the eggs in a container with NO holes and just opening the container for 30 sec or so once a week.
If you notice that it's still moist in 2 weeks, you probably have it just right.
Short answer, yes. Keep it "moist" enough, not to dry and not wet. They don't need much moisture.
If you find that you need to add water, carefully remove the egg for a moment while you mix in more water until it is how it should be...then put the egg back.
Good luck