Hi again.
I automatically assume with this forum that people are in the USA.
The ducklings really need to be left in until they are dried off somewhat - normally 24 hours. However, with my first hatch 14 months ago I had to remove the first hatched after about 8 hours as she was bombing around the small incubator, crashing into the other eggs and causing mayhem. As long as you are quick so as not to lose the humidity, then you can remove when you think it is OK. Just make sure your brooder is really nice and warm. and handle with real care as they are very fragile at this stage. From what I have read, the humidity is most important when the eggs have externally pipped. If you open the incubator whilst eggs inside have only just externally pipped then you run the risk of them shrink wrapping. I've had this happen with my second hatch even though the humidity was good and I hadn't opened the incubator at all! Just saw a couple of eggs which had externally pipped but were struggling after 48 hours to make any progress and the membrane around the pipped part of the eggs was very dry and yellow.
To be honest - this is my fourth hatch and every single one had been different. I think you just have to be patient, use common sense, or ask for help if you are unsure.