What is shelf life of an Inventory Item?

As per Wikipedia:

“Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or just no longer on a supermarket shelf (unfit for sale, but not yet unfit for use).

You need to enable the Batch Tracking option to capture the Shelf life of the Item.

Items whose shelf life has passed are treated as Dead Stock