From a store stocking perspective, the rapid advance of new products from Games Workshop is untenable. Thankfully, Games Workshop understands its own efficiency requires models to be regularly discontinued, much to the dismay of fans. New products theoretically release at roughly the same pace as we should be discontinuing old product, in a zero sum game. Figuring out what to discontinue is the trick.
Figuring out what to order is also a trick, a combination of skill and intuition. We have weekly releases, combined with a forced blackout pre-order period until the models are already on the train across the country. We generally fly blind, relying on past sales patterns to predict future results. Or we cheat a little and find a way to get informal or even formal pre orders from customers. This results in overstock as a way of life, or lately, ignoring releases if customers are indifferent, or sales patterns show no interest at all (Warcry this week). So how do we decide what in our 40K line stays and what goes once it's here?
Every store stocks differently. Also, every store stocks differently in their stocking lifetime. If you have a store now and you have a rigid idea of how you stock a line, just give it some time. When I first started, I carried a minimum range of GW stock. Three years later, with a huge store, with our local GW store closed and my main competitor retiring, I carried every Games Workshop model produced. A couple years after that I added Forge World from England, marking it up 10%, just to satisfy hungry customers. I was selling resin parts in display cases. At one point a competitor popped up specializing in 40K at a discount, and I pulled way back on my inventory as sales flagged (they're gone now). Lately I'm somewhere in the middle. There is no one answer or strategy. Local supply and demand drive my stocking strategy.
As a stockist store, I carry every required model. Are there ones that perform so poorly I would like to drop them? Sure, I've got five model kits I would like to dump, but I can't (three are Warhammer Underworlds). This is fantastic. It's $135 worth of product, which is a small opportunity cost for the benefits of the various GW programs. This wasn't always the case.
Sometimes this dead stock number can be thousands of dollars. The stockist benefit to customers is you can always find a core group of models at a store like mine. Does GW define that core well? It can be hit or miss, but it's mostly a hit. Companies can define their core on what they wish to sell, as opposed to what actually sells (Privateer Press). GW, in its current incarnation, is good with defining a strong core. It works for both of us.
All the other stock must serve the local community. This is a hard pill to swallow. I would like all the Orks or Tau on the shelf at all times, but once my customers have had a chance to buy what they need, it's increasingly difficult to stock for the casual who buys from us irregularly. Keeping a "coherent collection" of models of a particular army often falls apart, if you don't have new customers, with new needs, constantly visiting. With events functioning, but the public still wary of gathering, my sales are great, but new customers are harder to acquire. This is a game that for a good percentage of customers, requires new opponents on large tables in public spaces.
How do we know what 40K stock to drop? This is where sales performance metrics come in. Once a week I'll get a report of inventory that has stopped performing and I have to decide what stays and what goes. This report is overly generous, and if a title shows up, it's truly deceased. Those five core stockist items must stay, obviously, but 20 other items were deemed unworthy this morning, that should have gone. Five of those 20 were added to our online clearance section with some regret. 15 were given a pass, because I deemed them relevant ... for now.
So my store, and likely most stores, are going to have a core collection you can count on, new releases that are still fresh (this trade is "front list driven") and a collection that represents the current needs of their local 40K community. If as a customer, you shop irregularly, or you cross shop, don't be surprised if you find what's available makes no sense. We're using your sales patterns to predict the future, and with unpredictable sales patterns comes a mismatch of inventory to customer needs. I'm not placing blame, but this is what you get and I can't do anything about it. This is all we can do and it's why multiple stores exist, surviving on imperfect information (mine and yours). It's how I pay my mortgage, so certainly don't feel bad for me.