A problem with Spell Containers

[The_Fixer]

You misunderstand me.

First, this is a Rego Vim effect using that general guideline, not a MuVi effect, so AFAIK, it is fine with spontaneous magic:
Create a conduit or container for spells with level less than the level + 5 magnitudes of the Vim spell
I use this corebook guideline, and, IIRC, it's been stated already that the ritual is for the potentially infinite duration, and nothing else.

Second, I don't want it to create containers left and right, I want one item to be able to hold one spell, period. But, if you give the effect range: touch, you create a container in something for the spell's duration. This is so much more efficient than what I want, at the cost of a simple magnitude, that I wonder what reasons there may be for that not to be.

Hum... Consider this spell (pure coïncidence, this is fun), using the same guideline, with duration Sun:

@Erik Tyrrell

Crossbow with an Incantation Trigger
ReVi Gen
Range: personal, Duration: Sun, Target: Individual
Crossbow with the Incantation Trigger stores another spell or spells in the caster's body until that spell is triggered or until the next sunrise or sunset. The stored spell is triggered when conditions specified at the time of casting Crossbow with the Incantation Trigger come to pass. These conditions must include the casting of yet one more spell. When the triggering spell is cast all of the spells stored in the Crossbow with the Incantation Trigger are cast at the target of the triggering spell (if the stored spells do not have sufficient range or if the target of the triggering spell is an inappropriate target for the stored spells, the stored spells are cast with no effect).
Only one Crossbow with the Incantation Trigger can be placed or the caster. Any number of spells can be stored within the Crossbow with the Incantation Trigger providing that their total level does not exceed the level of the Crossbow with the Incantation Trigger + 15. If someone tries to dispel the Crossbow with the Incantation Trigger but fails the stored spell is cast upon them. At the end of the Crossbow with the Incantation Trigger's duration the stored spells are dispelled. The Crossbow with the Incantation Trigger is also dispelled when it releases its spells.
Ranulf typically uses Crossbow with the Incantation Trigger to store a copy of skin of wax that was cast in a beneficial aura and set it to cast on the same target as his next Pillum of Fire. (He would love to learn ceremonial casting specialization for Skin of Wax from a cult of Mercury colleague within his house but he isn't yet sufficiently well informed to know of this technique)
(Base general +2 sun)

This uses the guideline I mentionned, the one used by Watching Ward, with range personnal and duration sun.

I wanted an item with a similar effect (save that the conditions wouldn't include the casting of another spell), the only difference being moon duration. So far, everything's fine.

Problem is, if you do like with the watching ward, and give it a R: Touch duration, you then create a container in something else. So, so long as the items are different, you can keep on creating containers. This isn't an huge problem with D: Dun (although it lets you equip your grogs with an host of one-shot magical items), but it is one with duration: moon, as the increased duration means you can stockpile some more, so instead of having one item holding one spell, I could make, say, 10 different containers.