Do Commendations do anything, besides being mission objectives?
Do expeditions "regenerate"? If you completely explore the map and do all the expeditions available, is there any benefit to keeping the expedition center?
Commendations are currently only used to fulfill mission objectives related to them.
Expedition points of interest don't currently regenerate, so once you finish the expeditions, you can safely sell the Expedition Center. That may change at some point in the future, but probably not before launch.