In the space world, to be able to fly the next new mission, you have to have flight heritage from the previous mission. But if you don't fly the previous mission…it's kind of a chicken and egg thing.
We would like to have students and other engineers exercise and operate the spacecraft after the biology has been completed for at least some of that time. Of course, if a critical system were to fail or wear out, like the batteries or communications radio, then that's it … since we do not have a lot of redundancy in the design.
When we're in Sun, we run on the solar cells and charge the batteries. In eclipse, just the batteries power the spacecraft.