My parents always gave the example of budgeting in a little extra for things that are on sale that you can always use but won't go bad (like paper products,) or things that might be a rarer find and need to be stocked up on.
I used to clean out a shelf of everything I needed or wanted to buy as well if I had the money.
But a post here on CC from a member I highly respect changed my mind.
This CC member wrote that they were caring for other members of their family all with just their own paycheck, and they often didn't have the money to get some of the things they needed, only to find the shelves empty when they finally did have the money.
This person ended their post by asking readers to please consider leaving a few items for others who can't get there right away or don't have the money when things are fully stocked. I've been on both sides of the coin, so this struck a chord in my heart.
Now I usually leave a few items on the shelf and pray that it helps the next person. I see this as similar to when Boaz commanded his servants to purposely pull out extra grain and leave it in the fields for Ruth to pick up for herself and her mother-in-law, Naomi.
But, this is just my own personal conviction.