I think now I would intervene, specially if the duckling internally pipped a few days ago, there may be a problem with it's oxygen/carbon dioxide levels.
I recently helped a few chicks out, only because of a 5 hour power cut, I normally never assist a chick out. I candled carefully to locate the beak then knocked a piece of shell out (in the round end of the egg) I peeled a little membrane, damped the shell with warm water, left an hour then repeated removed another tiny bit of shell and membrane. They do dry out very quickly once the shell has been broken and you have to watch the membrane doesn't shrink wrap the chick/duckling, which will impede breathing and mobility.
Watch carefully for any bleeding, stop immediately if you see any.