I don't understand why people say things like a despawn timer would hurt the market for kraken drops... There is no market for kraken drops as the drops don't go outside of the group it goes to. I do agree though that making it more susceptible to siege damage is a good alternative.
Demand is larger than the supply, and therefore the external market of the Ink Sac is priceless outside of the factions that can compete with it, but eventually people will stop needing them. It won't be in the next Kraken, it won't be in the next 30, but eventually it won't be needed in-house, meaning (theoretically) eventually there will be a stockpile of them. There's no use having a stockpile of the item but there will always be a use for more gold.