Guys let's face it! are you thinking WE should teach Geobra how and what to sell?? Really? They have been in the market for over 30 years and I don't think they loose a dime out of the choices they make wether themes are on sale for 2 years or 10.
They are not supermen. They put their pants on in the morning one leg at a time just like the rest of us.
If they really knew what they were doing we would never have seen themes flop the way they have.
And you'd better believe they've lost a few dimes on those themes. And they will be very reluctant to repeat those mistakes.
The themes that are the olde stand-bys are the ones that keep them afloat are farm, horse ranch, pirates, knights, construction (to a certain degree but last year's sets show even that isn't cut and dried as a stand-by - kind of like the western sets), city life, dollhouse, princess, fire and police.
The other keep coming and going which means that 1) Geobra is willing to risk some things to try to expand and hit new areas and 2) they really do not know what they are doing or every single theme they produce would be a 'stand-by'.
As for time being a factor for knowing what to do, I think we just need to read any newspaper from North America from the last two years (and ask all the people who lost their jobs) that just because a company has (had!) been around for many decades (or centuries) does not mean they have a clue what they are doing today and have gone out of business and bankrupt.