Well, I'm fine with making all auras last until the end if the player's turn if they move out of range, but I don't see it as working improperly, if the player is worried about distance, then they use it. If they are not, they don't. (That said, I could also see adding other aura-augmenting feats that extend the range, persist the effect, etc.)

I also want to mention, I hate using rounds-after expressions (one of the things I like about 4e, and agreed with the devs about, personally).