We are actually keeping the keets in with the chicks until they are about 12 weeks old or so...maybe 18 weeks. Then we will consider running them loose on the property during the day (we have very few predators in our area, thankfully - other than our two hawks) and calling them back to the roost at night. We'll see how it goes. Don't know until we do it exactly how things will play out.
And, the crossing is apparently very, very, very rare. And, the results are infertile, so you don't have to worry about it being something ongoing.
My FIL had a prize bull that cost him something like $50k back in the late 50s. Something like that - can't think of the exact price, but it was staggering to me...anyway - he had that bull all of, maybe two weeks? Then it got gored in the "important bits" and he lost his fertility....he wound up being a very expensive "marker".