For me, that is far too long.
Especially with this description from their launch.
I think the maximum time should be 7 days without an exo.
Also, 5 days is too long to keep them up. I think everyone is aware that after a day most of the exo exclusive resources are gone already (except the really difficult to get ones). So to leave it there for another 4 days is a bit of a waste.
Get it down after 3 days and get another one up there!