Conures mating constantly=no eggs...ever

by Jade
(San Diego Ca)

I have two conures, Male (Jack-Jack) is a sun conure and the female (Violet) is a jenday conure. I got them both 3 years ago. They are both free roaming, meaning they have a cage with a playtop that is never closed unless they are not being supervised or at night. They have a nesting box hung inside their cage that they roost in every night, and they also go in it during they day to play and laugh.

They also have an outdoor cage where they go out and get some sun and fun during the day in the backyard. Their diet is Kaytee parrot mix every day, friuts (apples, pears, mango, pineapple, lime, etc) 3 times a week alternating with veggies (corn, broccoli, carrots, peas, etc) also 3 times a week. Now that we've covered history setup and diet...here's my question...

Once they have turned 2, they started mating. They have been actively mating now for over a year and have never produced any eggs. Just today I caught them mating 3 times in the back yard and that is an everyday thing. They have both been sexed and found to be male and female. Why no eggs?