Can I combine effects of 19 Deathwines?

Question

Let's say that I am a level 10 Arcanist. I cast Deathwine two times to affect 20 potions of Cure Light Wounds, costing 1000 gp. Then, "the first necromancy spell you cast within the next minute is cast at a higher caster level", so I spend the first 9 rounds using both my Move and Standard actions to drink those Deathwines. On the 10th round, I use my Move action to drink the 19th Deathwine, and then cast a Necromancy spell with a +19 bonus to its caster level.

Since the bonuses to caster level is untyped, those bonuses should stack.

On the other hand, this sounds like really cheap cheese, allowing e.g. a level 5 Cleric to easily create an 18-HD Necrocraft if enough gold is available. Also, the spell doesn't explicitly say that the bonuses stack.

So, how does it work?

Answer 1

No.

While untyped bonuses do stack, a bonus from the same source does not.

From the Glossary under bonus

Bonuses without a type always stack, unless they are from the same source.

As mentioned by Baskakov_Dmitriy I can help clarify the difference between stacking and non-stacking sources.There are other places where this is talked about, but I will take my own stab at it.

The full Glossary definition of bonus

Bonuses are numerical values that are added to checks and statistical scores. Most bonuses have a type, and as a general rule, bonuses of the same type are not cumulative (do not “stack”)—only the greater bonus granted applies.

The important aspect of bonus types is that two bonuses of the same type don’t generally stack. With the exception of dodge bonuses, most circumstance bonuses, and racial bonuses, only the better bonus of a given type works. Bonuses without a type always stack, unless they are from the same source.

Also from the Glossary we have the definition of stacking, which sadly does nothing to really clear this up.

Stacking refers to the act of adding together bonuses or penalties that apply to one particular check or statistic. Generally speaking, most bonuses of the same type do not stack. Instead, only the highest bonus applies. Most penalties do stack, meaning that their values are added together. Penalties and bonuses generally stack with one another, meaning that the penalties might negate or exceed part or all of the bonuses, and vice versa.

The magic rules have two sections on stacking.

First is Bonus Types

Usually, a bonus has a type that indicates how the spell grants the bonus. The important aspect of bonus types is that two bonuses of the same type don’t generally stack. With the exception of dodge bonuses, most circumstance bonuses, and racial bonuses, only the better bonus of a given type works. The same principle applies to penalties- a character taking two or more penalties of the same type applies only the worst one, although most penalties have no type and thus always stack. Bonuses without a type always stack, unless they are from the same source.

And then we have combining magical effects. Now this area spells out all the different circumstances where stacking can occur. For multiple castings/drinkings of deathwine it would fall under Same Effect More than Once in Different Strengths. Its under this ruling that the non-stacking aspect becomes apparent which is that all the deathwines are equal for the strength of the effect (or take the highest CL), so any of them can have their effect. Yes they are all active, but as the condition(s) activate, only one provides the +1 CL to your next spell. The rest activate and are simply unable to provide further bonus.

The end result is that this is a case of a ruling that should be obvious and was never directly written down, but implied in many locations. The same spell even if from a different caster, counts as the same source.