I'm afraid that the answer is rather down to earth, boring and sobering. It's a question of production-capacity and money. Geobra can only produce a certain amount of sets at one time. In other words new sets in means old sets out. It would be very dangerous for Geobra indeed if they would continue to produce all the sets...
As a hopefull note in the side-line. They don't throw out any mold; but keep them aside for possible future use. As can be seen in the re-use of the Katana in the Ghost-pirates.
Geobra doesn't do licensing Just as part of their business principles.
You are right.
Even so, I'd love to see some sort of "secondary collector agenda", like "hey: next year we're going to launch this again for you, collectors". It sounds like nonsense, because what happens nowadays is exactly the contrary: without agenda, we are afraid and counting down the day of the discontinuing of our favourite today's collection.
The logic of the market is that you have to produce something new to launch on Christmas, so it will sell, and make them money to pay Zirndorf. That's all right, not to mention that the production is turned back to children. That's all right as well.
It's sad, though, that we can't have some sort of cicle of launching again the themes, Either because they disappear, get rare (which may be an unconcious interest of the market (...)), as because those who don't have DS in their countries have to keep making calculations of when and how to make it happen to get bits or to compose sets and scenes that they'd like to, when it'd be easier to open Amazon.com, and send for a
Tailor's House 
aaaah--
aaaah!
, (
). Or even go to the Lojas Americanas, at the corner (Brasilian "Target" ...), and get one, even if divided into 10 in credit card ... (Oh, smokes! Good that there isn't this possibility!!!
haha!)
---
I love to see the mermaids in the catalogue. They go so well with the Romans!, heavens! And they go fine with pirates as well. Too bad I'm short of money, or I'd already gotten some
I like the ghost pirates as well. However, my priority, due to lack of resourses, are still some other things (4444 still, and hope they'll maintain it in catalogue time enough for me to get one ...) as well as I have to raise the money to make my DS order through a playmofriend who lives in the US, who's volunteered to help me with this.
But I'll survive, I'll survive
Gus
