My 1500 iron disappeared and a random dude said It has a 14 day limit or something.
That’s correct. After two weeks, your iron resets. You can save it by voting more or spending it before it expires. If you keep voting until you get more iron from a vote streak, the timer resets to 14 days.
There’s no way to store your iron, so keep voting to ensure you don’t lose it.
Hope that clears things up!