I'm curious whether there's any way to avoid flicker in a magic item absent making it a permanent effect. I'm thinking of Bilbo's ring as an example, a ring that turns you invisible when you put it on, but stops working as soon as you take it off.
Clearly this would be a PeIm effect like Veil of Invisibility with a Touch range, Concentration duration, Individual target, and unlimited uses, with possibly a trigger to start the effect (putting the ring on your finger). The concentration would be maintained whenever the ring was worn, but would stop when the ring was removed. (Which also neatly prevents more than one person from using the effect at the same time.) So far, so good.
But according to the rules (ArM5 core rules, p. 99) "Effects left to their own concentration start to wear off at sunset and sunrise. At these times the wielder must concentrate on the effect for a few moments to perpetuate it until the next sunrise or sunset, whichever comes first." Presumably the ring provides the needed concentration. Of note, the rules even say that this "effect is useful for things like invisibility rings, which have their effect when put on, and then maintain concentration and invisibility until removed."
As I understand conventional wisdom, however, this need for concentration would cause a flicker at sunrise and sunset. (Do I have that correct?) But so far as we know, Bilbo's ring didn't flicker at any time. When you had it on, you were invisible; when you took it off, you were visible again. Is there any way to replicate that effect in a way that doesn't cause flicker? Again, I know I could make it a permanent effect to avoid flicker. But we can assume I don't want to be permanently invisible. Is there a way under the rules that I can make a ring that keeps you invisible across the sunrise/sunset boundary without flicker?
Now, I realize that it's possible to use Moon duration to avoid flicker at sunrise/sunset. But that has two disadvantages: (1) there would still be flicker, albeit only at moonset of the latter of the new moon and the full moon; and (2) Once I put on the ring I'd be invisible for the entire Moon duration, even if I took off the ring, which is not the effect such a ring is supposed to have.
I understand that the answer to my question might be no. And while that's disappointing (and runs counter to the very example of an invisibility ring given in the rules), at least it's an answer I can work with.
Any thoughts from the gallery would be appreciated.