I guess this has been suggested many times before but I'll throw it out once again because I think it's needed.
Right now, the only information you get when upgrading a building is a number floating on top of the map. Way to often, that number is hidden by a tree or another building leaving you clueless about how long there's actually left. I have one picture to show both the problem and the suggested solution.
So, who can tell me how long is left before my level 5 improved storehouse is done? I think I might be able to see a six on certain zoom levels but the first digit is a mystery.
So the solution? Put one of the bars in the window as shown in the picture. It's the exact same as the one used for production. In fact, I just copy pasted it from a copper mine. Then give it a time to finish when you mouse over it just like how the one that shows production time works. Considering the amount of information you have on pretty much all other aspects of the game, I see no real reason to hide information on upgrades. At the very least, please move the numbers to float on top so you have a clue on how long it's left on an upgrade.