Just to be perfectly clear, with "leave-it-and-lose-it" I meant "Should a target leave the circle, the spell effect ceases". This need not be because the spell is necessarily broken; it may just cease to operate on the target, as in a type 2 spell, and restart as soon as the target re-enters the circle.
What I think it should be avoided in any case is that if you have a Circle spell affecting some targets for D:Moon, those targets can march off for a week affected by the magic, until someone erases the Circle and has the magic go poof 200 miles away. To avoid this "spooky action at a distance", and the ugly behaviours it engenders, I would either rule Circles operate as other containers (type I spells are unaffected by what happens to the Circle after casting) OR (better, in my view) rule "Circle spells never work on targets outside the Circle" -- that's what I mean with leave-it-and-lose-it.