First of all, it is not true that es is for permanent factors and está is for temporary ones. This is an over simplification. For example, if you want to say that Mexico is in North America, you might think that you should use es, because Mexico's location is permanent (short of an act of God). However, está is the correct word.
You can use está to locate something in physical space (here, there, on the moon, etc.) and es to locate it in time so if you want to say that the party is next week or was yesterday you would use a form of ser not a form of estar.
Now admittedly sometimes this rule of "temporary vs. permanent" may work out, but there are plenty of exceptions. You would say "Maria es abogada" even though she can change careers if she wants. Similarly, you might say "El coche es rojo" even though you can paint it a different color if you choose.