The KonMari method discourages stockpiling, but I can't resist a hot deal on something I know I'm going to need down the line. It's depressing and almost physically painful to imagine regularly paying full price for something because I didn't stock up when I could have and consequently have run out of it.
I do think that it's harder to have the kind of stockpile I'm thinking of in Japan. Houses and apartments there are tiny. We live in a townhouse that's not particularly big, but you could fit three Japanese bedrooms in our master bedroom!
Where I think I've gone wrong in the past when it comes to stockpiling and tidying is not storing like items together. I've had cleaning items scattered throughout the bathrooms, the kitchen, and the cabinet under the wet bar, paper goods in various cabinets, etc. In doing so, I haven't been able to keep track of how much of something I have on hand already.
So now I'm following the KonMari method of keeping my stockpile in one place. All of my cleaning supplies are now in the cabinets under the wet bar. I've rearranged the personal care supplies to keep the shampoo bottles together, the lotions together, etc. I'm working on rearranging my paper goods stockpile - as I declutter and create space, I will have a large enough space in a closet to store all of our paper towels together. (Bulky items like that have been spread throughout the house precisely because they're bulky.)
Being able to see everything of one category that we already have helps me to see whether or not I should stock up when a sale comes along. For example, I now know that we are running low on body wash, but have plenty of shampoo.
How do you manage your stockpile?