Originally Posted by
Psyren
That lets you change to a different choice from the same list (i.e. a different feat, not a different spell.) It does not let you change the choices within the choice you made. So you can't change "Expanded Arcana: Spell A" to "Expanded Arcana: Spell B" as that would be choosing the same feat (even if you are trying to change what that feat gives you.) Similarly, you can't change "Improved Eldritch Heritage (Arcane) - New Arcana - Spell A" to "Improved Eldritch Heritage (Arcane) - New Arcana - Spell B" as that is the same feat again.
What you can do is go from "Expanded Arcana: Spell A" to "IEH(A) - NA - Spell B." But the first time you do that, your choices for both of these feats are locked in, so every time you switch back to them you will get the same two spells (A and B) every time. That's still two floating spells per day, so still very useful, but not unlimited versatility.