Almost everything in your kit has a shelf life.

Ferro rods decompose from contact with atmospheric moisture. Batteries get stuid with age to. All of your meds will reach the point they don't anything. Even bullion cubes can get blue and furry. Anything rubber or leather will suffer dry rot if forgotten, metal containers and blades will rust.

Matches should be swapped every year or every other year if they've been dipped. All of your food items (other than MREs, lifeboat rations, and freeze drieds) and batteries should be rotated annually.