# How many effects can an item maintain concentration on?

If you have an item that casts an effect with concentration duration, and the item maintains concentration on that spell, how many times can the effect be cast and still have the item maintain concentration?

My thoughts are it must be either once, or an infinite number but I can't find a ruling anywhere?

Joke aside, in our game we decided that:
a) since the item needs the user to briefly concentrate on the effect to perpetuate it at sunrise and sunset, there is only a relatively small number of effects that can really be kept up indefinitely, about a score (we assume "briefly" means a round, and allow a "renewal window" of a Diameter, the literal duration of a sunrise or sunset).
b) other than that, there is no limit, since no limit is stated (save, of course, the number of times the item can be activated in a day; once/round is about seven thousand activations between a sunrise and a sunset -- more or less depending on the season and the latitude).

I'm pretty sure it's once.

Is it a gut feeling or is there something else in support of this statement?

Nothing hard and fast, but two things from the rules:

1. The singular is used repeatedly, as though there is a single effect that may be turned on and off, not many that may be turned on and off.
2. Why would anyone ever use D: Sun in a magic item unless paying for constant otherwise? You'd always gain more for no extra cost using D: Concentration and maintaining it. This way there is more balance.

Hmm.
I disagree about 1; it seems to me it's just talking about that particular "instance" of an effect without being unnecessarily verbose.
But I find 2 very convincing. Not necessarily about how the authors intended it, but about how it should be read. (Ok, you could nitpick about really low magnitude effects, but even I won't go there).
I'll bring this up to my gaming table. Thanks!

My rule is that an item may maintain concentration on any number of castings (up to the per day limit obviously) but that the user may only maintain concentration at sunrise/sunset on one.

Indeed.

Reading ArM5 p.99 Effect Modifications Concentration, you see, that the capability of a device to concentrate is per effect.

• If you instill multiple effects, for each one you decide and pay for the concentration capability separately.
• But for each effect with that capability, that capability is treated consistently in the singular.
• In particular, the explicit mention "This allows the wearer to end the effect at will, and start it again if the device has uses left." hints at one concentration at a time per effect with that capability.

With that reading, you could indeed install an identical effect with concentration capability twice into the same item. Not very economical, but it could surprise your sodales: that item indeed appears to maintain concentration at the same time on two uses of the same effect.

Cheers