U need 4 - Co-OP on Xbox Live - Endure can take from Hour & 15 minutes on Alpha Site to like 2-1/2 hours on Lost Platoon.
Deja-Vu also 4- Co-Op Xbox Live depending on skill of ur players between a 1/2 hour to 1-1/2 hour.
I'm not sure on all being on 1 Xbox but I don't think so these challenges came our for Recon but also to promote socializing on Xbox Live- I have them but if U would like another player message me on Xbox- G.T.>RoTTieweiler - Good Luck
[Edited on 04.27.2011 4:08 AM PDT]