What species? The incubation length varies depending on species quite a bit. You'll know they are close when you start to see the eggs cracking, once they begin sweating your within days. The babies will slit the egg then eventually crawl out and begin exploring, you can leave the container sealed the babies will be fine just want to check it everyday once they are close to term and remove them as they hatch. Communal raising is fine if that's your only option but I wouldn't keep them all together, once group size is over 4-5 it's very hard to tell who's doing ok and who may need more attention. If they are all together its much harder to pick out the problems and as they get to the 2-3 month mark they will start doing damage nipped tails and such.