I have noticed that after reaching a certain level (about 40 in my case) there is no point to build expert buildings.
It waste of time and resources, because you can get ANYTHING by trade with much, much lower cost.
The buildings are far to expensive, not to mention upgrades …
Some upgrades do not have real payback. For example, there is no added-value to upgrade provision house to level 4 as speed increase is hardly to notice (I upgraded it and I regret lost resources).
To sum up, IMHO there is something wrong about cost structure for expert buildings.
Nothing to encourage me to build them; I do a lot of adventures just buying needed crossbows or damascene swords…
Developers should thing about that, maybe even do something about that, hopefully not killing or limiting trade possibilities.
Take care,
Mechanix