We know (based on the availability of the various lettered editions) that there are ~25 people who currently buy every lettered edition, and probably each buy a numbered edition too. I assume that a number of them are on the DRE train as well, but have no indication of how many. I think that a much smaller group of people purchase all the prints (based on the fact that most prints are ~100 total copies and most are still available in one or both sizes).
I'd be curious to know what percentage of the ~250 numbered slots have been filled by people who plan to purchase every book. My guess is that this is currently a much higher percentage than most, if not all, of the other small genre presses (thinking mainly about Centipede Press, Sub Press, Cemetery Dance, PS Publishing, and Charnel House, with Letterpress Publications a bit too early in the process to tell). I think this is why Suntup Editions is the only press that requires you to buy every edition to maintain a specific number with pre-order status. All the other presses have a variety of tracks (King tracks, specific author tracks, specific series tracks, etc.) that allow you to maintain a number under certain circumstances and only request it in others.
I would bet that at some time in the future there will be a tipping point, at which time there will be a minority of sales coming from customers who buy every book and a majority coming from a mix of customers who buy many but not all books plus customers who buy only books that they have a special interest in. I'm sure that this is the current case for all the other small presses (maybe not Charnel House), and I'm also sure that it's related to the much greater output of all those presses (also excepting Charnel House). However, Suntup does maintain a consistently higher price point for both limited and lettered editions, which makes it extra hard to try to predict how many yearly releases will eventually result in the tipping point! Is it 4 books? 6? Probably if it were to go up to 12 books per year it would "tip".
I hope that at that point (if it comes), Paul might consider a model similar to what Centipede Press uses (other presses might do this as well, but I don't know): if you agree to a subscription in which you purchase all of the books, you are guaranteed the same number, access to all releases, and a discount off the list price.
But all of this only considers the buyer's standpoint, not the publisher's!
Those concerns would probably include:
1. When is profit maximized?
2. When is the ability to spend as much time as necessary on each book compromised?
3. What is the optimal work/life balance for the proprietor?
And those are probably all different points! My gut feeling is that (2) is the current priority and (3) is probably a higher work/life ratio than normal, given that we all know that Paul was a collector first, and very much prioritizes the needs and desires of collectors. But let's give him ten years and see if he gets a little jaded
Of course this is all rampant speculation on my part. Would be curious to hear other people's thoughts...
(And their book choices as well!)