Just to warn you, our beloved developer, Lilith Game
I will definitely quit the game and request ios refund if you are going to increase the lvl cap of the castle from 40 to 50 or to 41 whatsoever.
It is okay that you guys gain your profits by creating news elements of the game or providing better experience for the players. However, lvl 50 castle or lvl 60 heroes or anything like that are just manipulating numbers. It takes less than a minute to increase the castle cap from 40 to 50 for you guys.