Ancalagon
Dusty Dragon
You bring up an interesting dilemma. The best answer I can think of is to have it be limited by the amount of ingredients a player can take from a given area. Either they'll have found all the mature herbs/the checks to locate more get too high, or the local herbalist shop runs out of their current stock because the player bought it all. I don't know what the hard numbers on those limits should be, and it may be different for different campaigns (some feature more travel than others), but that's essentially a more realistic way to put a cap on the maximum number of items a player can stockpile without relying on encumbrance.
We are in agreement on the need for a special resources that is limited, and that the number of resources is a great way to balance the alchemist character.
*however*, what should that number bit is an unanswered question. If you look at the old thread ( http://www.enworld.org/forum/showth...ive&p=7323842&highlight=bloodroot#post7323842 ) this is essentially what I was asking. I never got a very satisfactory answer. Some people just couldn't accept the premise.