I''m sure every player has reached this point:
You don't have enough fire crystals. In order to get more, you need to either get more crystals from levels or get more money (also achieved by going through levels). As you go through the levels, your equipment will be fully heated. However, since you don't have the fire crystals to forge your equipment, they just end up staying at full heat as you get more heat from that moment on.
So, what happens to the heat when your equipment is fully heated?
...Nothing. The heat would just dissipate and be useless.
What I'm proposing is this: