Angels are created beings (as are we). They have not existed from all eternity - they were created at some point. Thus, the circumstances of their existence is subject to change (as are ours - we have an earthly existence, and a more permanent existence yet to come).
The Catholic Church formally teaches very little about angels. But all Catholic and Jewish theologians are of the unanimous opinion that angels were created in a state that lacked the Beatific Vision (an awareness of the true nature of God), because no intelligent creature could rebel against God if he were fully aware of God’s true nature (which would, in essence, deprive angels of free will, because the choice would be so flippin’ obvious as to render any other possible choice patently unacceptable).
We speak of angels as residing in “heaven” and retroactively apply that concept to angels who had not yet made a free-will decision to either submit to God or themselves. But, whatever “heaven” these “new” angels inhabited, it is not the same as envisioned today (where each inhabitant enjoys the Beatific Vision).
