Salve Sodales!
Happy Winter Solstice holiday to you!
The title basically is the question, can I enchant an effect with multiple stacking fast triggers?
For example:
Ring of Oh Shit! ReCo 35
Cast Wizard's Leap with a +9 initiative modifier
(Base 15, +3m Fast Trigger x3, +1m uses 24/day)
It's not specified, but I don't see why not. After all, you could have a very quick speed on a spell with Finesse. The real restriction is that this doesn't count as a fast casting... It's still an action rather than an interrupt.
I agree with @temprobe.
First, it isn't written like penetration. Compare:
For every level you add to the effect’s level, that effect gets +2 Penetration.
v.
The effect gains a +3 Initiative modifier. This adds +5 to the level of the effect.
Usually if something is supposed to be repetable you see something like the language in the prior case. I don't see that language in this case at all.
Second, this seems so abusable. +0.6 initiative per point added in the lab. Raising item penetration is +2 per point added in the lab, and it's considered very powerful. Sure, its initiative is only 0.3 times as fast. But compare this to what it takes to improve these with spells. Penetration increases with 2 Arts, 1 Ability, and some other things. Initiative increases with 1 Ability, while fast-casting increases with 2 Abilities. We might say 1.5 Abilities to average those out. Roughly speaking, spell penetration can be increased around 4x the rate that spell initiative can be. As this penetration applies across a lot more things (Arts go to a lot, and Penetration goes to any spell) while initiative is only from a Mastery, though fast-casting is from that and Finesse, that means you get even more out of the penetration stuff than 4x the rate. Even at 4x the rate, Fast Trigger is improving notably better than Penetration. Penetration is considered very powerful already, and this would be well beyond Penetration.
From another view, think how easy it is to get +12, for example. +20 to a Lab Total. A bit tough, but totally doable. How hard would it be to get +12 to your initiative when casting a spell? Mastery to 12 in a single spell taking only Quick Casting is a massive investment. No one is ever going to get there.
My conclusion: It's not vaguely implied by the rules, and it is so abusable so easily that it shouldn't be done.
So initiative mostly matters in two main circumstances: You are trying to kill an opponent first, or you're fast-casting to self-defend. If you're trying to kill an opponent first - you'll almost always be better off investing additional penetration in the device, and if you're trying to fast-cast to self-defend, a device is useless. Yes, there are scenarios where +12 to initiative on a device is useful, but not that many. Defensive spells that aren't used as an interrupt are one such instance - but in almost all instances, such spells would be better off cast with D: Sun prior to needing them, with your action used offensively instead. That leaves what? Leap of homecoming? I'd still tend to prefer a good finesse score and the option of fast-casting it from spell mastery on most characters... Even for a linked trigger item that reacts to something offensively which might be nice to try and trump a fast-cast defense... you'd almost always be better off with more penetration too.
I'm with Callum: it's not implied by the rules, and could be very powerful sometimes, so no. The analogy with Finesse is unreliable, as that's limited by the triangle cost. So if you want to rule it in, I'd suggest at least making the cost go up in a triangular way.
Personally, I don't like the idea that a bigger lab total can always win initiative.