I did find this in the help section In Game
"I can’t use my Treasury
The Treasury is a temporary vault that holds resources collected from your Star Bonus and War Win Bonuses. It’s capacity is finite: meaning you need to collect the Treasury’s loot to successfully store more.
Make sure to empty the Treasury regularly by pressing “Collect”, to move those resources into your proper Storages. Only resources in your Storages are used for upgrades, troop training, etc…"
What and when does the word regularly refer to though?