The number of items I stockpile feels about right, both for keeping track of in my mind, and for the amount of storage space available in our house for stockpiling.
Still, I really hate having to run out to the store at the last minute when I run out of a crucial ingredient. I have had several traumatizing experiences dragging young and crabby children through the store halfway through dinner prep!
The compromise for me is to keep One Extra of most of the non-perishable items in my pantry. When I use up the mayonnaise, or the hoisin sauce, or the brown rice, I pull out the One Extra from the pantry, and add the item to the grocery list on the fridge, one of the little things I do to keep myself more organized.
Typically these items are condiments and cooking items, and for the most part, it's not worth the savings to buy a bunch of them on sale, and anyways I don't have a lot of space to stockpile items unless they are used frequently. Some of these items cost pretty much the same amount no matter when I purchase them (such as groceries from Trader Joe's).
For example, I recently made Chicken Adobo with bok choy in the crock pot. I used up my apple cidar vinegar, the opened my One Extra one. I promptly added cidar vinegar to the grocery list--this system works better when I'm not cooking in a hurry. I'll buy just a small bottle on the next grocery trip because I don't use it very often. I'm not stressing about getting to the grocery store in time because I still have a mostly full bottle.
I also saw that my paprika was getting low, so I added that to the grocery list too. I dont keep One Extra for spices and flours, because I like my spices to be relatively fresh, and some take a long time to use up. Instead I add them to the list when I see that the quantity on hand is running low.
This system has been working really well for me for several years now. I love that I can reach into the pantry and pull out whatever I need! The system would work even better if I didn't have to spend precious minutes finding things in the pantry. I'm hoping to deal with that problem soon!