I know why there was such fascination by Toyota in the 50s with American supermarkets. They fascinate me too (even though it takes me too long to find stuff). You mean whatever we sell, we replace? Replenishment based on consumption. No more, no less. Except for seasonal adjustments, there is always the same amount of soup in the soup aisle. There is never some in aisle 3 and some overflow in aisle 4. Whatever we buy, they replenish. Daily. This is how I think of one-piece flow. I also like the fact I can have it exactly when I want it, without lead time. 99% of the time, it's there. Aha!! This proves the fact that by eliminating long lead times, you can actually see demand for what it really is....relatively stable over time. (This isn't true for new products...their demand hasn't been established yet). If they sell 100 clam chowders, they don't "make" a truckload!
You need to resist the urge to cave in on 2 very common arguments in favor of overproduction. First, what about the freight cost of buying less more often? Second, if I buy 1000 I pay $1.50 each, but if I buy 5000 I pay $1.35 each! This is the same argument that says to make more because the setup takes a long time. My answer to this argument is......yes. There WILL be items that make more sense to buy more of, and there will be things where it makes more sense to keep making more due to a long set up (until you do SMED!) But, if this is your business strategy for more than a handful of items you buy or make, much of your cash will be in buckets you can't get to!
I have a fun game to play. Make believe all of your products, raw materials and information waiting in any Inbox is impatient, like people at the motor vehicle department. Make believe that at anytime, they will be tired of waiting and throw a fit, cause a scene. Or, pretend that all of your products (and raw materials) are fresh fruit! Talk about just-in-time!