Shouldn't be infinite or nonconsumable, I mean, durability on equipment isn't infinite. Repairing is a nagging thing in gaming, why not remove it in D3 too? [/sarcasm]
However, making a maximum stacking of arrows/bolts of 5000 to 10,000 per pack should make most people happy, as it will be usable for dozens of minutes, possibly even a couple of hours (cough, increased stack size anyone?) without bothering the player.