Would this work?

[Sensten]

Poisoned adamantine (for bypassing DR, +1 attack for masterwork) or viridium shurikens using Flurry of Shurikens could be a scary combo. But poison is so expensive it would be like throwing shurikens made of money. Enter Abundant Ammunition. Abundant Ammunition replaces any mundane ammunition, including shurikens. Poison is mundane.

The thing is, I can't find a solid answer to how long poison lasts after it's applied. If I applied poison to a handful of shurikens in the morning and used AA each time, what would happen? Would they last all day? Purple worm poison has a DC of 24 and costs 700. Drow only costs 75 with 13 DC and might put someone to sleep.

I could also use the Poisoner's Jacket, which creates three vials of poison a day (<= 300g) but go inert after an hour. But, since AA replaces it, does that refresh the amount of time before the poison goes inert?

And I wouldn't have to shell out for shurikens again either.

Any other mundane addons? Or is the whole idea just infeasible? What would need to happen to make it viable?

[HaraldKlak]

I am not sure that I would allow it.

While abundant ammunition replaces the weapon itself, it doesn't state that any additions (such as poison) is replaced.

Some GMs might choose to allow it, yet I feel that it allow some very cheap poisons (the best of them normally being limited by their price).

[Dabbler]

I would say that poison in general lasts for around an hour after being applied. On the other hand, would you want to walk around with a handful of poisoned spikes in your pocket? No, nor me. Apply poison just before use is my advice.

[Grizzly the Archer]

Arrows, or shurikens as you like, are the best application for poisons. If you make viridium durable arrows, then the viridium won't break unless it hits the creature.

Abundant ammunition wouldn't extend the poisons volatility for a longer time. It merely copies whats currently in the bag. It is stated that poison lasts until it is struck (used in an attack) or is wiped off.

Applying poison:
"One dose of poison smeared on a weapon or some other object affects just a single target. A poisoned weapon or object retains its poison until the weapon scores a hit or the object is touched (unless the poison is wiped off before a target comes in contact with it).

Applying poison to a weapon or single piece of ammunition is a standard action. Whenever you apply or ready a poison for use, there is a 5% chance that you expose yourself to the poison and must save against the poison as normal. This does not consume the dose of poison. Whenever you attack with a poisoned weapon, if the attack roll results in a natural 1, you expose yourself to the poison. This consumes the poison on the weapon. If you have the poison use class feature (such as from the assassin prestige class or the alchemist base class), you do not risk accidentally poisoning yourself when applying poison."

Emphasis mine. So, until the shuriken or arrows are used, they last.

[Secane]

Abundant Ammunition won't copy the poison. It only affects the ammunition.
The line "this spell replaces any ammunition", clearly states it affects ammunitions only."

Similarly if you blanch an arrow, cast AA and fire that arrow. You get a replacement arrow (an ammunition), but not the blanch (an alchemical substance) on it.

PF's rules does not work on the principle of "if something is not mentioned, then surely it can be done."

Just because Abundant Ammunition does not have a list of "does not work on... etc...etc." listed with the spell, does not means the Abundant Ammunition can work on additional substances applied to ammunition.