Max upgrade on castles.
Up to level 20, you'll get either more nerds, more nerd-holding capacity, or better defences with every upgrade. After that, you get a castle wall with every upgrade.
Forum Discussion
If you put max nerds on a castle and the player defends, you lose all those nerds and don't get any more reward than if you'd only used one nerd. My personal strategy is to put one nerd on a building per town (one nerd per town). If I see a town that isn't being defended, I'll put five nerds there (one per building). Spreading out your nerds gives you the best chance of victory and even if the players defend, you'll still earn more gold/elixir than if you unload a ton of nerds on one building.
I think a lot of players use this strategy. My personal preference but others my have different ideas.
8)
I think a lot of players use this strategy. My personal preference but others my have different ideas.
8)
