Related: Fake explanation, Guessing the teachers password, Understanding your understanding, many more
The mental model concept gets used so frequently and seems so intuitively obvious that I debated whether to bother writing this. But beyond the basic value that comes from unpacking our intuitions, it turns out that the concept allows a pretty impressive integration and streamlining of a wide range of mental phenomena.
As far as predictions go, reusing concepts from elsewhere might allow you to quickly make predictions about something with limited accuracy, but have a difficult time improving on the predictions. Without recycling understanding might take longer, but ultimately allow for more accurate predictions. Recycling seems to favor good enough solutions.
The compartmentalization parallel is interesting - I'll have to think more about it.