Sun conure eggs take between 3-4 weeks to hatch. Since the eggs are laid every other day, you need to count from when the last egg was laid. If none have hatched within 33 days of the last egg being laid, then the eggs are either infertile or there is another issue. You are correct that first clutches almost always fail with any captive bird species. The parents are learning and tend to make mistakes. There are a lot of factors involved with breeding success. The birds need to be old enough to be breeding. In captivity, they tend to become mature at a younger age than in the wild, but they are still not ready for breeding. Your birds should be at least three years old. When you let them breed too soon, they are often not ready to settle down and care for eggs and chicks. They can develop bad breeding habits that will ruin them as ever being good breeders such as breaking or eating the eggs. Your birds must be on a nutritionally balanced diet such as pellets or our foraging diets. A seed mix will not provide the nutrition they need. You should also offer dark leafy greens and chopped veggies. When they are set up for breeding as they are now, you should be offering them an egg food daily. This can be a commercial egg food or you can cook an egg with the shell washed, crushed and cooked with the eggs. This is very important because it replaces the protein and calcium the female loses when forming eggs, and it is also something they need when feeding chicks.
I do not recommend trying to incubate the eggs. An incubator can cost between $100-$300 or more. While you may have read that you can make an incubator, this is not a good idea. The eggs have to be kept at the right temperature and humidity, and have to be turned about 8 times a day. Any mistakes with temperature, humidity or egg turning can cause the embryo to die or cause the chick to not develop properly. This can result in a weak, stunted chick. Or sometimes the chicks can seem healthy and then die suddenly due to something not being right with it internally. It is very hard to hand feed a chick from day one, and there is a high mortality rate. Even the most experienced breeders will lose most chicks that are fed from the first day. It’s best to let the pair learn from their mistakes. Some pairs will never be good breeders. If they fail 3 times or more, the pair should not be bred again.
If these eggs do not hatch, you need to remove the nest box or block the entry, and rest the pair for about 6 months. You should only allow two clutches per year. In the wild they only breed one time per year. In captivity, they do not receive the environmental changes that signal the end of breeding, so it is your responsibility to prevent them from breeding over and over. Laying eggs is hard for the female, and if she is allowed to breed without resting in between clutches, she can end up dying from laying eggs too often.
Thank you for asking Lafeber,