While we do save your cart for you for up to 4 weeks, any items that you have added to your cart are not put on hold for you unless you complete checkout.
If you have noticed that an item you had in your cart has since disappeared, it is more than likely because it was a low-inventory item that has since sold out (someone else completed their purchase that included your item).
We remove any out of stock items from active saved carts.
You may also notice that an item your cart has changed price since you added it.
If we have ended a promotion, or started a new one, since you last checked your cart, the item will reflect the most up-to-date pricing in your cart when you come back.