It depends on whether you have a separate incubator for hatching and how much hassle you want to put up with. Eggs that are close to hatching need vastly different conditions from eggs that are in earlier stages of incubation, and you simply can't provide that if you've got eggs all in the same incubator developing at different stages. So if you've only got the one incubator then I'd say you're asking for a lot of trouble and probably a lot of unhatched ducklings that die at late stages in development. What's going to happen is that the earlier eggs are going to get ready to hatch and they're going to need a higher humidity to keep the membranes from drying out and trapping them in the shell. They will also need to stop being turned & not have access to a turner where they can get their legs & wings trapped. You can provide those conditions in a separate incubator, but if you only have one, you'll have to provide the same conditions to your eggs that are still developing--and that need to be turned and need a lower humidity in order to develop the right size air cell for hatching. Also, the ducklings that hatch are going to make a BIG mess in the incubator--hatching gunk & poop all over the eggs, and they're going to shove them all over the place & tap at them. No big deal if the eggs are near hatching, but those earlier in incubation can get all kinds of infections and disease from being pooped & slimed on.
Hopefully, you've got another incubator, and you'll be fine--just follow the instructions already provided above. Otherwise... stop adding eggs, and keep posting--somebody will help you navigate the difficulties and get the best result possible. This is a great bunch, and we've all made mistakes, so don't worry--just do the best you can.
