I'm trying to puzzle this one out, and have been for over a decade. Because this isn't the only game where I've seen this 'feature' though that's a genuinely kind word for what I really think of it.
What is a valid reason to lock down a player's production for a week while a building upgrades? It's a lot more restrictive with chains like the barracks than it is with other chains, but the question is posed as a general one: why would you think that this is a good idea?
I can see arguments for realism, for encouragement of planning, etc but none of them actually weigh in very well against the fun lost by players when this occurs. It's a forced timeout for the player from an activity that they expressed a desire to have more of by paying the material costs for the upgrade process in the first place. So they're stopped from engaging in that process, whether it be building soldiers or grinding flour.
And I wonder about player retention during such forced timeouts.
Is there a metric in place to even see how many level 30-somethings who finally manage to get the resources for that first level 5 building and start the upgrade only to discover a different game to play during that week-long timeout and never come back to Settlers Online?
I have to ask because I can not for the life of me understand why you would want to force people to not play?
(I didn't mention the possibility of gem buyout because I don't know anyone who has used it for a week-long upgrade. Seems like a real longshot of an answer to the question. I doubt there's much revenue in that stream....)
So - hit me with the answer. What is it?