Do you get annoyed when you want to put in more than 35 unstackable food in an sign? We should get some plugin that allows you to say something like: /signadd <item> <Amount> and you culd just stack it up instead of waiting for years.
This isn't so much a problem with signs, it's a problem with stores. There's no reason that a player couldn't reserve an entire floor of a store for selling the same item. 10 signs, all selling the same item, is significantly more than anyone should be able to sell in a day. If you can move more than 300 bread in a day, I suggest you're selling it too cheaply. Honestly, infinite-holding signs would make competition between stores impossible. The largest players in the economy could make small, centrally located shops with nearly infinite inventories. The only competition would be the server store. Were that the case, what incentive would there be for players to open shops? Each player's store is currently restricted by spacial constraints. Unlimited storage will remove that restriction, causing all sorts of economic problems. I'm compelled to suggest this is a bad idea.