All backpacks in the game, including the Crafted Improvised Backpack (w/ Burlap), get 6 hours of default persistence. However, the Crafted Leather Backpack only gets 2 hours of default persistence.

Multiple users have complained about this, as it is often assumed that backpacks get 6 hours. For instance, it is a common tactic to deposit a backpack in a hiding place before engaging in a firefight, just in case one dies. With Crafted Leather Backpack, this very common strategy cannot be used because of the inconsistency.