I do my changes every 3 days when im not busy....I tend to slip up sometimes and have gone as long as a week and a half...they aren't too picky or fragile, at least I don't see them to be more so than any other fish, but they do like consistency.
as far as baby discus, I really haven't had time to commit to make sure they are successful..i let them do what they gotta do in the community tank, and if I get young...well, great but I have no where for them to grow out
kings discus is really good in that most stores may have a few discus...one or two of each variant that they have, kings may have several tanks full of the same variant, so you have a lot more leeway to be picky- like I mentioned, temperament is as important to me as appearance and you never see that at some places where there may be only one or two discus in a tank