Class Evolution Switching

Sagittarius

Astellian
Sep 27, 2019
28
51
13
If I unlock a class Evolution to 5 Stars and then switch to a different class is the progress toward the 5 Stars in my original class kept or lost? Do I have to pay XP to switch back to the 5 Star class that I just finished leveling or am I free to switch between all of them as much as I want with all of them are at 5 Stars (assuming when I get them all there)