I am gonna be in the same boat soon - raising two last forges to 20 and will be out of mats soon. they need to have a sustainable iron sink. I am a quest whore, and I want to finish that collect iron V mission, and if storage is full, I cant collect any more iron and I cant progress in the mission - that is gonna bug me lol.
by the EnP lore, “feeding” heroes and troops is not actual feeding, it is rigorous training which consumes “fed” heroes/troops. well, you need food to sustain them and iron to make armor and weapons for training! I wish they made you select food and/or iron to spend on training, with like a sliding bar between 100%food/0% iron to 0%food/100%iron with options in between, with foos/iron ratio similar to production rates.