Anna, you said for me to do this awhile ago, did you not? ;3
Just like in real life, items you buy in the Pokemart eventually wear down to the point where you can no longer use them. We wouldn't want a pencil to last forever, now would we? Now you are wondering how to roleplay this? Example:
15 classes after buying a pen
"Hitomi used her pen for every class to write down notes. Now, 15 classes after that, her pen was nearly out of ink. Every other word, she would have to shake the pen to get the ink down to the ball. "GAHHHH, I have no more ink!" She exclaimed.
R.I.P. Pen.
Anyways, here's the list of items and how long they can be used. And keep in mind these are about the time they should be gone.
Pokechow Box x1: 1 RP week [after feeding every RP day which you should.]
Pokebone: 2 RP weeks
Poketreats Box x1: 3 RP weeks
HB2 Pencil: 15 classes
Pens: 35 classes
Notebook: 60 classes
Eraser: 50 classes
Notebook Paper: 3 classes
Staple x1: 2 classes
Notepad: 60 classes
Aww, I made it ugly. Someone fix it please.