We've been told by one breeder we can't always count on egg production in every year. Thanks for your input. I have heard so many times about proven pair of hyacinths who when checked out by a vet they are either too young to breed or were the same sex, or are now so old that their repoductive organs are even looking old. Its difficult to say how long birds will breed. I know some that will try and take your head off while on the other hand I know of birds that will allow their owner to check on the chicks while they sit quitely in the box.
Every bird behaves differently.